[SerialConsole] Change to require custom boot diagnostics

[adrianabedon]

---

The following commands now check to see if the specified VM uses custom boot diagnostics.

az serial-console connect
az serial-console send nmi
az serial-console send sysrq
az serial-console send reset

This checklist is used to make sure that common guidelines for a pull request are followed.

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• Have you run python scripts/ci/test_index.py -q locally?

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

About Extension Publish

There is a pipeline to automatically build, upload and publish extension wheels.
Once your PR is merged into master branch, a new PR will be created to update src/index.json automatically.
The precondition is to put your code inside this repo and upgrade the version in the PR but do not modify src/index.json.

[ghost]

Thank you for your contribution adrianabedon! We will review the pull request and get back to you soon.

[yonzhan]

SerialConsole