Rename feature flags.

[starcke]

This renames the feature flags from:

    "codeQL.dataExtensions.editor": true,
    "codeQL.dataExtensions.llmGeneration": true,
    "codeQL.dataExtensions.disableAutoNameExtensionPack": true,
    "codeQL.dataExtensions.extensionsDirectory": true,

to

    "codeQL.model.editor": true,
    "codeQL.model.llmGeneration": true,
    "codeQL.model.disableAutoNameExtensionPack": true,
    "codeQL.model.extensionsDirectory": true,

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[robertbrignull]

I found one remaining reference in a comment:

• vscode-codeql/extensions/ql-vscode/src/model-editor/extension-pack-picker.ts

  Line 229 in 11ca60f

  // Get the `codeQL.dataExtensions.extensionsDirectory` setting for the language

But otherwise this looks good to me as a code change.

I've asked one question on the internal issue about whether it's ok to not have a transition period where we support both feature flags.

[starcke]

I found one remaining reference in a comment

I'll do that in a followup to not drag this one out. I had to run CI quite a few times to get it though yesterday.