Remove underscores and capitals from all JSON options

[multiplemonomials]

Summary of changes

This is a followup to my earlier Pydantic schemas PR. It fixes all of the hundreds of warnings that are now being printed about options with incorrectly formatted names.

There should (TM) be no code impacts from this change, as the configuration system will "normalize" names into the new format, so you can still e.g. override a option with the old name containing underscores. However, I did find a minor bug in the previous PR, which is that it didn't handle the case of options with underscores in their namespaces. That has been fixed here.

Impact of changes

Migration actions required

Documentation

None

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Pull request type

[X] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[X] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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[multiplemonomials]

This has been removed as this is available in its own repository: https://github.com/PelionIoT/mbed-client-cli