feat(internal/{appsec,traceprof}): reduce dependency on google.golang.org/grpc

[darccio]

What does this PR do?

Isolates testapp (only used by internal/traceprof) and replaces metadata.MD with a simpler map[string][]string.

Stacked on #4182.

Motivation

Reduce the scope of our dependencies. In this case, grpc is an indirect dependency through go.opentelemetry.io/collector/component and others.

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[bot]]

Benchmarks

Benchmark execution time: 2025-12-19 12:26:04

Comparing candidate commit 38c30ba439d0cdefe42926f459deca396bfe0419 in PR branch dario.castane/apmlp-494/testapp-isolation with baseline commit ea97c5952b594a7d6e52d3834056ece9a53e3045 in branch main.

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

[darccio]

/merge

[dd-devflow-routing-codex[bot]]

View all feedbacks in Devflow UI.

2025-12-19 12:11:23 UTC :information_source: Start processing command /merge

---

2025-12-19 12:11:33 UTC :information_source: MergeQueue: waiting for PR to be ready

This pull request is not mergeable according to GitHub. Common reasons include pending required checks, missing approvals, or merge conflicts — but it could also be blocked by other repository rules or settings. It will be added to the queue as soon as checks pass and/or get approvals. Note: if you pushed new commits since the last approval, you may need additional approval. You can remove it from the waiting list with /remove command.

---

2025-12-19 12:11:48 UTC :warning: MergeQueue: This merge request was unqueued

[email protected] unqueued this merge request

[darccio]

/merge -c

[dd-devflow-routing-codex[bot]]

View all feedbacks in Devflow UI.

2025-12-19 12:11:39 UTC :information_source: Start processing command /merge -c