docs: instrumentation telemetry usage [LANGPLAT-352]

[emmettbutler]

This change adds minimal documentation explaining how contributors should use Instrumentation Telemetry.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

docs/contributing.rst                                                   @DataDog/python-guild
docs/index.rst                                                          @DataDog/python-guild
docs/spelling_wordlist.txt                                              @DataDog/python-guild

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 274 ± 2 ms.

The average import time from base is: 275 ± 2 ms.

The import time difference between this PR and base is: -1.5 ± 0.09 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 1.987 ms (0.73%)

ddtrace.bootstrap.sitecustomize 1.311 ms (0.48%)

ddtrace.bootstrap.preload 1.311 ms (0.48%)

ddtrace.internal.remoteconfig.client 0.633 ms (0.23%)

ddtrace 0.676 ms (0.25%)

ddtrace.internal._unpatched 0.031 ms (0.01%)

json 0.031 ms (0.01%)

json.decoder 0.031 ms (0.01%)

re 0.031 ms (0.01%)

enum 0.031 ms (0.01%)

types 0.031 ms (0.01%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-06-12 15:26:29

Comparing candidate commit 63875be in PR branch emmett.butler/telemetry-docs with baseline commit fd2bcdf in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 539 metrics, 3 unstable metrics.