docs: add missing tests for getting started examples

[injisg]

Description

Add test_metrics.py and test_otlpcollector.py to validate the metrics_example.py and otlpcollector_example.py scripts.

• test_metrics.py: Validates all 7 metric types with specific expected values
• test_otlpcollector.py: Tests OTLP collector example with graceful timeout handling

Fixes #4001

Type of change

Please delete options that are not relevant.

• [x ] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• [x ] Executed both tests in my environment

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• [x ] No.

Checklist:

• [x ] Followed the style guidelines of this project
• Changelogs have been updated
• [x ] Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: sginji / name: sginji (081bf0a, f249def, 3da34f0)
• ✅ login: xrmx / name: Riccardo Magliocchetti (5fb6cbd)

[xrmx]

I think the issue was about running examples code in CI and not about writing some new tests

[injisg]

I think the issue was about running examples code in CI and not about writing some new tests

My bad! 😄 i'll update!

[injisg]

I think the issue was about running examples code in CI and not about writing some new tests

@xrmx - I do see that the existing tests run as part of CI. Example run from another PR that's open: https://github.com/open-telemetry/opentelemetry-python/actions/runs/15904348585/job/44855076756?pr=4659

Is there more to be done to add these tests to the CI pipeline? I see that they are configured here 🤔

[injisg]

@xrmx just checking in again - can you help clarify the requirements?

[xrmx]

@sginji please fix the lint errors and setup pre-commit and we should be good to go.

[injisg]

@sginji please fix the lint errors and setup pre-commit and we should be good to go.

@xrmx I've fixed lint and setup pre-commit too.