Enforce cross-boundary imports for `pageEditor` references as error

[twschiller]

Context

• Follow up to https://github.com/pixiebrix/pixiebrix-extension/issues/4887
• Make imports of @/pageEditor an error, except for:
  • Within the @/pageEditor module
  • If file follows Foo.pageEditor.tsx? naming convention. E.g., LocalProcessOptions.pageEditor.tsx
  • Allow importing the @/pageEditor/documentBuilder/render directory. See discussion at: https://github.com/pixiebrix/pixiebrix-extension/issues/4887#issuecomment-2171513908. E.g., rename that directory to "shared" and have the rule allow imports of `shared" subdirectories