chore(sentry apps): Add telemetry to token exchange

[Christinarlong]

The endpoint was already giving us 403s so let's get some more context to why (perhaps a before and after comparison) 👀

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 93.10345% with 2 lines in your changes missing coverage. Please review.

:white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/sentry/mediators/token_exchange/refresher.py	91.66%	1 Missing :warning:
src/sentry/mediators/token_exchange/validator.py	80.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #79257      +/-   ##
==========================================
- Coverage   78.34%   78.34%   -0.01%     
==========================================
  Files        7125     7123       -2     
  Lines      314477   314605     +128     
  Branches    51356    51413      +57     
==========================================
+ Hits       246384   246483      +99     
- Misses      61650    61653       +3     
- Partials     6443     6469      +26