[compiler] Derive ErrorSeverity from ErrorCategory (#34401)

With #34176 we now have granular lint rules created for each compiler
ErrorCategory. However, we had remnants of our old error severities
still in use which makes reporting errors quite clunky. Previously you
would need to specify both a category and severity which often ended up
being the same.

This PR moves severity definition into our rules which are generated
from our categories. For now I decided to defer "upgrading" categories
from a simple string to a sum type since we are only using severities to
map errors to eslint severity.

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[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34401).
* #34409
* #34404
* #34403
* #34402
* __->__ #34401

DiffTrain build for [60d9b9740d77bd2715f5f725245093a23f95e347](https://github.com/facebook/react/commit/60d9b9740d77bd2715f5f725245093a23f95e347)