feat: add process tags to tracing payloads

[rarguelloF]

What does this PR do?

Adds a new _dd.tags.process trace-level tag (equivalent to the following DataDog/dd-trace-java#8698), which will allow users to rename their services.

The initially collected tags for Go are:

• "entrypoint.name"
• "entrypoint.basedir"
• "entrypoint.workdir"
• "entrypoint.type"

But these could be extended in the future, and might be collected and added by some contribs (e.g. the grpc service name or similar).

By default the collection of these tags is disabled, and is enabled using the environment variable: DD_EXPERIMENTAL_PROPAGATE_PROCESS_TAGS_ENABLED.

There will be a number of follow-up PRs adding this data to the payloads for:

• Stats
• Profiling
• Remoteconfig
• DSM
• Telemetry

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 golangci-lint run 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: 2025-06-02 12:58:34

Comparing candidate commit 9c8a429 in PR branch rarguelloF/process-tags-tracing with baseline commit f2441d3 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 21 metrics, 0 unstable metrics.

[rarguelloF]

/merge

[dd-devflow]

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2025-06-02 09:11:34 UTC ℹ️ Start processing command /merge

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2025-06-02 09:11:38 UTC ℹ️ MergeQueue: queue is disabled

Added to the queue but the mergequeue is not enabled for now.

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2025-06-02 12:48:04 UTC ❌ MergeQueue: This merge request was updated

This PR is rejected because it was updated