chore(profiler): Add deprecation warning for session functions

[sentrivana]

We're deprecating the short-lived start_profile_session and stop_profile_session functions in favor of start_profiler and stop_profiler, respectively.

The functions will be dropped in 3.x, see #4170

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.56%. Comparing base (f6db981) to head (56c4324).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4171      +/-   ##
==========================================
+ Coverage   79.49%   79.56%   +0.06%     
==========================================
  Files         141      141              
  Lines       15732    15735       +3     
  Branches     2675     2675              
==========================================
+ Hits        12506    12519      +13     
+ Misses       2379     2369      -10     
  Partials      847      847              

Files with missing lines	Coverage Δ
sentry_sdk/profiler/continuous_profiler.py	86.03% <100.00%> (+0.45%)	⬆️

... and 5 files with indirect coverage changes