feat(transport): Add a timeout

[sentrivana]

For some reason, we don't define any timeouts in our default transport(s).

With this change:

• We add a 30s total timeout for the whole connect+read cycle in the default HTTP transport
• In the experimental HTTP/2 httpcore-based transport there is no way to set a single timeout, so we set 15s each for getting a connection from the pool, connecting, writing, and reading

Backend SDKs in general set wildly different timeouts, from 30s in Go to <5s in Ruby or PHP. I went for the higher end of the range here since this is mainly meant to prevent the SDK preventing process shutdown like described in #4247 -- we don't want to cut off legitimate requests that are just taking a long time. (I was considering going even higher, maybe to 60s -- but I think 30s is a good first shot at this and we can always change it later.)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.53%. Comparing base (fb6d374) to head (f135ac3).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4252      +/-   ##
==========================================
- Coverage   79.54%   79.53%   -0.01%     
==========================================
  Files         142      142              
  Lines       15905    15907       +2     
  Branches     2723     2723              
==========================================
  Hits        12652    12652              
- Misses       2385     2389       +4     
+ Partials      868      866       -2     

Files with missing lines	Coverage Δ
sentry_sdk/transport.py	80.04% <100.00%> (+0.09%)	⬆️

... and 6 files with indirect coverage changes

[aivarsk]

You missed the second pool options implementation around lines 772 for HTTP2 I guess

[aivarsk]

And just a side note - I don't know what are the Sentry SaaS response times but 5 seconds might be too little for the read timeout. I think other software uses 15 seconds by default.

[sentrivana]

Gotcha, still working on this, not final yet -- planning on adding the timeout to the other transport and also need to decide on a good default

[antonpirker]

looking good! 🚀