Added performance benchmarking doc

[martinkuba]

Which problem is this PR solving?

Part of #4171

Short description of the changes

This PR adds a doc with instructions on how to add new benchmark tests.

[codecov]

Codecov Report

Merging #4169 (225e009) into main (5af8653) will not change coverage.
The diff coverage is n/a.

❗ Current head 225e009 differs from pull request most recent head f44530e. Consider uploading reports for the commit f44530e to get more accurate results

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[pichlermarc]

Added comment about the test:bench script, otherwise looks good 🙂

[martinkuba]

The current Lint/build failure does not seem to be related to this change (broken links in doc/tracing.md and doc/metrics.md).

The semantic conventions docs have been removed from the specification repo. I have updated the links here, but let me know if you prefer that to be in a separate PR. @pichlermarc

[pichlermarc]

The current Lint/build failure does not seem to be related to this change (broken links in doc/tracing.md and doc/metrics.md).

The semantic conventions docs have been removed from the specification repo. I have updated the links here, but let me know if you prefer that to be in a separate PR. @pichlermarc

Ah, I think having it in this PR is fine. Thanks for fixing it 🙂