Instead of relying on UNRESOLVED_REFERENCE directive for the whole file,
just render the unresolved reference right in the .txt testdata
This will allow to introduce multi-caret resolve testdata more naturally
Required for KT-65152 and KT-62695
Tests can now specify the code generated by a resolve extension from
within the test's testdata. Module-level directives control whether
resolve extensions are enabled for that module, as well as package names
and source shadowing regexes. File-level directives allow a `// FILE:`
block within the testdata to be converted into a KtResolveExtensionFile
and removed from the module as a whole. (This requires a new
`ModuleStructureTransformer`, because we need to be able to entirely
remove the files in question.)
Any test can add support for these directives by calling
`KtResolveExtensionTestSupport.configure` from within their
`configureTest` stanza. This allows this functionality to be used in
conjuction with any test base class.
^KT-59329
Roman Golyshev