internal/remoteconfig: support for DD_REMOTE_CONFIGURATION_ENABLED

[eliottness]

What does this PR do?

Introduces a new env var called DD_REMOTE_CONFIGURATION_ENABLED to disable remote config client side.

Motivation

Closes #3060

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.
• For internal contributors, a matching PR should be created to the v2-dev branch and reviewed by @DataDog/apm-go.

Unsure? Have a question? Request a review!

[datadog-datadog-prod-us1]

Datadog Report

Branch report: eliottness/DD_REMOTE_CONFIGURATION_ENABLED
Commit report: 6cde583
Test service: dd-trace-go

❌ 1 Failed (0 Known Flaky), 5120 Passed, 70 Skipped, 2m 54.57s Total Time

❌ Failed Tests (1)

• TestExchangeContext - gopkg.in/DataDog/dd-trace-go.v1/contrib/miekg/dns - Details

  Expand for error

   Failed
   
   === RUN   TestExchangeContext
       dns_test.go:47: listen udp 127.0.0.1:2020: bind: address already in use
       dns_test.go:85: 
           	Error Trace:	/home/runner/work/dd-trace-go/dd-trace-go/contrib/miekg/dns/dns_test.go:85
           	Error:      	Received unexpected error:
           	            	read udp 127.0.0.1:44849->127.0.0.1:2020: read: connection refused
           	Test:       	TestExchangeContext
       dns_test.go:53: 
   ...
  

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-02 11:08:22

Comparing candidate commit d9ea482 in PR branch eliottness/DD_REMOTE_CONFIGURATION_ENABLED with baseline commit 4f57a47 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 58 metrics, 1 unstable metrics.