Add support for httpx2

[sk-]

Problem Statement

httpx2 (https://github.com/pydantic/httpx2) seems to be the accepted community fork of httpx, specially given it's maintained by pydantic. This is even more true, when the author of httpxyz (a previous fork) blesses this new package.

It would be great if Sentry could add support for that package.

Solution Brainstorm

Given that both packages may be in use (specially while packages transition to this new fork), I think the best solution is to just copy https://github.com/getsentry/sentry-python/blob/2ce26d120b2ea8622bd463188fc6b4150aafdb2c/sentry_sdk/integrations/httpx.py and maintain a separate integration.

[linear-code]

PY-2502

[sentrivana]

Thanks for the poke @sk-! The new integration will be out in the next release, and we've made it auto-enabling to ease the transition for folks migrating.