[Enhancement]: Add `/wc-analytics/reports` APIs to the document

[ianlin]

Part of the task: pfKYZu-2C-p2

In addition to the WC REST API with the namespace /wc/v3, we've also introduced a set of APIs for WooCommerce Analytics under the namespace /wc-analytics. To improve the visibility of these APIs and avoid confusion with the legacy reports API /wc/v3/reports (used for the deprecated legacy reports), we will add the /wc-analytics/reports API to the REST API documentation. We will also clearly explain the difference between the legacy reports API and the WC Analytics API.

A shared branch feature/add-wc-analytics-reports-api-doc has been created and this will serve as a feature branch, meaning all subsequent PRs should be merged into this branch first, allowing us to release all the APIs document together.

The APIs we will be adding are as follows:

### Analytics > Products
- [x] GET [/wc-analytics/reports/products](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Products/Controller.php#L30) - #249
- [x] GET [/wc-analytics/reports/products/stats](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Products/Stats/Controller.php#L30) - #249

### Analytics > Revenue
- [x] GET [/wc-analytics/reports/revenue/stats](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Revenue/Stats/Controller.php#L37) - #250

### Analytics > Orders
- [x] GET [/wc-analytics/reports/orders](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Orders/Controller.php#L28) - #250
- [x] GET [/wc-analytics/reports/orders/stats](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Orders/Stats/Controller.php#L27) - #250

### Analytics > Variations
- [ ] GET [/wc-analytics/reports/variations](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Variations/Controller.php#L33)
- [ ] GET [/wc-analytics/reports/variations/stats](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Variations/Stats/Controller.php#L30)

### Analytics > Categories
- [ ] GET [/wc-analytics/reports/categories](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Categories/Controller.php#L28)

### Analytics > Coupons
- [ ] GET [/wc-analytics/reports/coupons](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Coupons/Controller.php#L30)
- [ ] GET [/wc-analytics/reports/coupons/stats](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Coupons/Stats/Controller.php#L30)

### Analytics > Taxes
- [ ] GET [/wc-analytics/reports/taxes](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Taxes/Controller.php#L35)
- [ ] GET [/wc-analytics/reports/taxes/stats](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Taxes/Stats/Controller.php#L29)

### Analytics > Downloads
- [ ] GET [/wc-analytics/reports/downloads](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Downloads/Controller.php#L28)
- [ ] GET [/wc-analytics/reports/downloads/stats](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Downloads/Stats/Controller.php#L29)
- [ ] GET [/wc-analytics/reports/downloads/files](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Downloads/Files/Controller.php#L32)

### Analytics > Stock
- [ ] GET [/wc-analytics/reports/stock](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Stock/Controller.php#L30)
- [ ] GET [/wc-analytics/reports/stock/stats](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Stock/Stats/Controller.php#L32)

### Performance Indicators
- [ ] GET [/wc-analytics/reports/performance-indicators](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/PerformanceIndicators/Controller.php#L30)
- [ ] GET [/wc-analytics/reports/performance-indicators/allowed](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/PerformanceIndicators/Controller.php#L88-L92)

### Export
- [ ] PUT [/wc-analytics/reports/(?P<type>[a-z]+)/export](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Export/Controller.php#L36-L40)
- [ ] GET [/wc-analytics/reports/(?P<type>[a-z]+)/export/(?P<export_id>[a-z0-9]+)/status](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Export/Controller.php#L50-L54)

### Import
- [ ] PUT [/wc-analytics/reports/import](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Import/Controller.php#L34-L38)
- [ ] PUT [/wc-analytics/reports/import/cancel](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Import/Controller.php#L47-L51)
- [ ] PUT [/wc-analytics/reports/import/delete](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Import/Controller.php#L59-L63)
- [ ] GET [/wc-analytics/reports/import/status](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Import/Controller.php#L71-L75)
- [ ] GET [/wc-analytics/reports/import/totals](https://github.com/woocommerce/woocommerce/blob/9297409c5a705d1cd0ae65ec9b058271bd90851e/plugins/woocommerce/src/Admin/API/Reports/Import/Controller.php#L83-L87)