feat(internal/config): Introduce internal config package

[mtoffl01]

…ct, ConfigSource object, and tests

What does this PR do?

Motivation

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.
• New code is free of linting errors. You can check this by running ./scripts/lint.sh locally.
• 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.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-11-04 17:27:41

Comparing candidate commit bfdaae7 in PR branch mtoff/config-revamp with baseline commit 9db3a3d in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 24 metrics, 0 unstable metrics.

[datadog-official]

⚠️ Tests

⚠️ Warnings

🧪 6 Tests failed

TestAssessSource from github.com/DataDog/dd-trace-go/v2/ddtrace/tracer (Datadog)

Failed

=== RUN   TestAssessSource
--- FAIL: TestAssessSource (0.00s)

TestAssessSource/invalid from github.com/DataDog/dd-trace-go/v2/ddtrace/tracer (Datadog)

Failed

=== RUN   TestAssessSource/invalid
    otel_dd_mappings_test.go:19: 
        	Error Trace:	/Users/runner/work/dd-trace-go/dd-trace-go/ddtrace/tracer/otel_dd_mappings_test.go:19
        	Error:      	func (assert.PanicTestFunc)(0x103a3df70) should panic
        	            		Panic value:	<nil>
        	Test:       	TestAssessSource/invalid
        	Messages:   	invalid config should panic
    --- FAIL: TestAssessSource/invalid (0.00s)

TestTracerOptionsDefaults from github.com/DataDog/dd-trace-go/v2/ddtrace/tracer (Datadog)

Failed

=== RUN   TestTracerOptionsDefaults
--- FAIL: TestTracerOptionsDefaults (0.28s)

View all

ℹ️ Info

❄️ No new flaky tests detected

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