DEBUG-3568 DRY transport options, remove HTTP.new method

[p-datadog]

What does this PR do?

Reduces duplication of existing transport code by removing the HTTP.new method which was identical for all transports and removing the code that copied agent settings into transport options.

Transport options are now explicitly enumerated (they are api_version and headers) instead of being a hash. This will make code that passed invalid or unknown options fail instead of silently doing nothing.

Motivation:
Preparation for chunking of dynamic instrumentation event submissions

Change log entry
None

Additional Notes:
This PR should not contain any API changes. The options style arguments have been replaced with explicit keyword arguments in some methods but the set of arguments accepted remains the same as before.

How to test the change?
Existing unit tests

[datadog-datadog-prod-us1]

Datadog Report

Branch report: transport-options
Commit report: 0097941
Test service: dd-trace-rb

✅ 0 Failed, 20624 Passed, 1373 Skipped, 3m 17.49s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-03-11 21:05:15

Comparing candidate commit 0097941 in PR branch transport-options with baseline commit 65b2901 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.70%. Comparing base (65b2901) to head (0097941).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4469   +/-   ##
=======================================
  Coverage   97.70%   97.70%           
=======================================
  Files        1379     1380    +1     
  Lines       83881    83813   -68     
  Branches     4251     4226   -25     
=======================================
- Hits        81953    81888   -65     
+ Misses       1928     1925    -3     

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