DEBUG-3700 Remove duplicated classes from Telemetry transport

[p-datadog]

What does this PR do?

Removes duplicated Core classes from Telemetry transport code.

Motivation:
As part of getting telemetry working for dynamic instrumentation, telemetry needs to work with UDS which is what shopist uses. Currently Telemetry only supports HTTP. Using the Core transport code will bring UDS transport to Telemetry.

Change log entry

None

Additional Notes:

This is the first PR of a series. the next one will add a Core-based transport. This PR should be quick to review and conceptually it is standalone.

How to test the change?
Existing unit tests

[github-actions]

Thank you for updating Change log entry section 👏

^{Visited at: 2025-04-10 17:30:19 UTC}

[datadog-datadog-prod-us1]

Datadog Report

Branch report: telemetry-transport
Commit report: c2308a7
Test service: dd-trace-rb

✅ 0 Failed, 20790 Passed, 1370 Skipped, 3m 37.67s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-04-10 17:54:23

Comparing candidate commit b723f99 in PR branch telemetry-transport with baseline commit 7e2eeea in branch master.

Found 1 performance improvements and 0 performance regressions! Performance is the same for 30 metrics, 2 unstable metrics.

scenario:profiler - stack collector

• 🟩 throughput [+156.567op/s; +158.106op/s] or [+5.733%; +5.790%]

[p-datadog]

The deleted telemetry code always returned nil for code, and code does not exist in the Core response class, therefore I changed reading of code to stringifying the response.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.73%. Comparing base (7e2eeea) to head (c2308a7).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4575      +/-   ##
==========================================
- Coverage   97.76%   97.73%   -0.03%     
==========================================
  Files        1405     1399       -6     
  Lines       86182    85903     -279     
  Branches     4357     4350       -7     
==========================================
- Hits        84258    83961     -297     
- Misses       1924     1942      +18     

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[p-datadog]

datadog-ci-rb uses one of the removed clasess thusly:

          begin
            require "datadog/core/telemetry/http/adapters/net"

            # patch gem's telemetry transport layer to use Net::HTTP instead of WebMock's Net::HTTP
            Core::Telemetry::Http::Adapters::Net.include(CI::Transport::Adapters::TelemetryWebmockSafeAdapter)
          rescue => e
            Datadog.logger.warn("Failed to patch Datadog gem's telemetry layer: #{e}")
          end

LoadError is not derived from StandardError and will escape the rescue above.

I will put back the file with a dummy class definition.