Fix startup crash caused by corrupted cookie store

[arpitJ-dev]

Description (required)

Fixes #6915

CommonsCookieStorage.load() previously allowed malformed persisted cookie data to throw during application startup, leaving both the main process and ACRA process in a persistent crash loop.

This change treats an unreadable cookie store as an invalid saved session. It keeps the in-memory cookie collection empty, removes only the corrupted cookie_store preference, logs the recovery, and leaves unrelated preferences intact. Valid cookie stores and the existing plaintext-to-encrypted migration behavior are unchanged.

Unit tests cover malformed and truncated JSON, JSON null, blank values, incorrect top-level types, invalid domain values, valid empty and populated stores, invalid individual cookies, unrelated-preference preservation, and repeated loading after recovery.

Tests performed (required)

• Ran the focused CommonsCookieStorageTest and adjacent JsonKvStoreTest suites on BetaDebug: 16 tests, 0 failures.
• Tested BetaDebug on a Samsung SM-S938U running Android 16 (API 36).
• Reproduced the original main-process and ACRA crash loop with a malformed persisted cookie store.
• Installed the fixed build over the same corrupted data and confirmed successful recovery and subsequent cold launches.
• Verified recovery for a bare string, truncated JSON, JSON null, a top-level array, an invalid domain value, and whitespace-only data.
• Verified that a valid empty JSON object remains accepted and retained.

Screenshots (for UI changes only)

Not applicable; this change has no UI modifications.