Add deprecation warning to AxClient

[saitcakmak]

Summary: Since this was our primary API for a long time, we should signal its removal with a deprecation warning before removing it for good.

Differential Revision:
D90390538

Privacy Context Container: L1413903

[meta-codesync]

@saitcakmak has exported this pull request. If you are a Meta employee, you can view the originating Diff in D90390538.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.73%. Comparing base (ceea2cb) to head (993f09e).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4749   +/-   ##
=======================================
  Coverage   96.73%   96.73%           
=======================================
  Files         582      582           
  Lines       60707    60718   +11     
=======================================
+ Hits        58722    58733   +11     
  Misses       1985     1985           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[meta-codesync]

This pull request has been merged in 5dccf83.