* When set to `true`, `hideDuplicateTextMateGrammars` will hide all grammars except whichever one the user has indicated a preference for — via `useTreeSitterParsers` and `useLegacyTreeSitter` settings, whether global or scope-specific.
* When set to `false`, `hideDuplicateTextMateGrammars` will show all grammars, even Legacy Tree-sitter.
…and create `useLegacyTreeSitter` for those who want to opt into the previous default behavior.
(Legacy Tree-sitter grammars will soon be removed, but this is a step toward that future!)
…along with a temporary `core.useExperimentalModernTreeSitter` setting.
If we truly planned to keep three different language modes around indefinitely,
changing `core.useTreeSitterParsers` to an enum would make sense. But we don't,
so it'd actually just be a gigantic pain in the ass to migrate one setting to
another of a different type.
When we ship modern-tree-sitter experimentally, we'll make it opt-in via the
temporary setting. When we make it the official tree-sitter implementation and
remove the legacy node-tree-sitter version, we'll remove the temporary setting
and just change the semantics around `core.useTreeSitterParsers`.
Reverting the addition of the `core.languageParser` setting is a chore, but it
prevents a _gigantic_ future headache.
