[SDTEST-160] API metrics

[anmarchenko]

What does this PR do?
Adds the following metrics:

• git_requests.search_commits
• git_requests.search_commits_ms
• git_requests.search_commits_errors
• git_requests.objects_pack
• git_requests.objects_pack_ms
• git_requests.objects_pack_errors
• git_requests.objects_pack_bytes
• git_requests.objects_pack_files
• git_requests.settings
• git_requests.settings_ms
• git_requests.settings_errors
• git_requests.settings_response
• itr_skippable_tests.request
• itr_skippable_tests.request_ms
• itr_skippable_tests.request_errors
• itr_skippable_tests.response_bytes
• itr_skippable_tests.response_tests

How to test the change?
Unit tests are provided

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 98.78049% with 2 lines in your changes missing coverage. Please review.

Project coverage is 98.84%. Comparing base (1ab2fd2) to head (b67a64f).

Files	Patch %	Lines
lib/datadog/ci/transport/http.rb	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #206      +/-   ##
==========================================
+ Coverage   98.83%   98.84%   +0.01%     
==========================================
  Files         251      251              
  Lines       11416    11526     +110     
  Branches      509      516       +7     
==========================================
+ Hits        11283    11393     +110     
  Misses        133      133              

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