[SDTEST-292] Retry HTTP requests on 429 and 5xx responses

[anmarchenko]

What does this PR do?
Expands failed requests retry logic for HTTP client in this library to be as follows:

1. If response HTTP code is 5xx, retry up to 3 times with exponential backoff
2. If response HTTP code is 429, retry up to 3 times, take backoff value from X-RateLimit-Reset response header (stop retrying if backoff value is over 30)
3. If response HTTP code is 4xx (but not 429), fail immediately without retries
4. If exception is raised due to network issues, retry up to 3 times with exponential backoff

Motivation
Better handling of transient server errors and rate limit hits: we have some requests failing with 429/503 according to internal telemetry

How to test the change?
Unit tests are provided for each of the above cases

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 98.59155% with 1 line in your changes missing coverage. Please review.

Project coverage is 98.88%. Comparing base (570d019) to head (82207ac).

Files with missing lines	Patch %	Lines
lib/datadog/ci/transport/http.rb	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #243      +/-   ##
==========================================
- Coverage   98.89%   98.88%   -0.01%     
==========================================
  Files         279      279              
  Lines       13524    13575      +51     
  Branches      620      625       +5     
==========================================
+ Hits        13374    13424      +50     
- Misses        150      151       +1     

Flag	Coverage Δ
	98.88% <98.59%> (-0.01%)	⬇️

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