Fix registering new metric categories from plugins

[fab-10]

PR description

This PR fixes an issue with new metric categories registered by plugins and enabled via metrics-categories option, since when the plugin registers them it is already too late in the startup process, and Besu fails reporting an unknown metric category option.
To fix this, the validation of the metric categories have been postponed to the moment we build the metric configuration from the metrics options, because at that point all is set.

Fixed Issue(s)

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• Considered documentation and added the doc-change-required label to this PR if updates are required.
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• For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• unit tests: ./gradlew build
• acceptance tests: ./gradlew acceptanceTest
• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests

[jflo]

fixes #7818

[jflo]

great move getting rid of the need for converters