With Parsoid now properly in core, that means the actual code identifying lint errors is also in core. Some parts of core, such as signature validation, also utilize lint errors.

As of 1.40, Linter is now a bundled extension, which means we generally recommend it for most instances. Given all of that, it seems like we should just merge the extension itself into core so that the logic isn't half in-core-via-Parsoid and half in an extension.

Specifically this means merging:

• the linter database
• Special:LintErrors
• API list=linterrors, meta=linterstats

Not sure if we need to retain RecordLintJob or whether it can be merged into one of the LinksUpdate jobs (related: T330036: Linter updates in a Parsoid-in-ParserCache world).