feat(ci_visibility): add rq_compressed and rs_compressed tags to request metrics

[gnufede]

Summary

• Adds rq_compressed and rs_compressed boolean tags to the request count metric
• Tracks whether HTTP request/response bodies were gzip-compressed
• Request compression state flows from BackendConnector._do_single_request through BackendResult.is_gzip_request to telemetry

Test plan

• Unit test for both compression tags present
• Unit test for request-only compression
• Unit test for response-only compression
• Integration tests for gzip request detection in BackendConnector
• All existing test_http.py assertions updated with compressed_request= parameter

Motivation

Per CI Visibility telemetry RFC: since gzip support was added for backend requests/responses, we need tags to distinguish compressed vs uncompressed payloads on metrics like endpoint_payload.requests, git_requests.search_commits, etc.

🤖 Generated with Claude Code

[cit-pr-commenter-54b7da]

Codeowners resolved as

ddtrace/testing/internal/http.py                                        @DataDog/ci-app-libraries
ddtrace/testing/internal/telemetry.py                                   @DataDog/ci-app-libraries
tests/testing/internal/test_http.py                                     @DataDog/ci-app-libraries
tests/testing/internal/test_telemetry.py                                @DataDog/ci-app-libraries