Link.hh: add Sensor accessor APIs (backport #2693)

[mergify]

🎉 New feature

Adds missing APIs

Summary

This adds SensorByName, Sensors, and SensorCount accessors to the Link class.

Test it

1. Build this branch
2. Run UNIT_Link_TEST
3. Run INTEGRATION_link

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

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This is an automatic backport of pull request #2693 done by [Mergify](https://mergify.com).