[AA] Allow specifying REx file contents in testdata.

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

analysis/analysis-api/testData/resolveExtensions/referenceResolve/singleModule/topLevelFunction.kt

@@ -0,0 +1,28 @@
+// WITH_RESOLVE_EXTENSION
+// RESOLVE_EXTENSION_PACKAGE: generated
+
+// FILE: extension.kt
+// RESOLVE_EXTENSION_FILE
+package generated
+
+// RESOLVE_EXTENSION_CLASSIFIER: GeneratedClass1
+class GeneratedClass1
+
+// RESOLVE_EXTENSION_CALLABLE: generatedTopLevelFunction1
+fun generatedTopLevelFunction1(): GeneratedClass2
+
+// FILE: extension2.kt
+// RESOLVE_EXTENSION_FILE
+package generated
+
+// RESOLVE_EXTENSION_CLASSIFIER: GeneratedClass2
+class GeneratedClass2 {
+    fun generatedClassMember2(): GeneratedClass1
+}
+
+// FILE: main.kt
+import generated.*
+
+fun main() {
+    generatedTopLevelFunc<caret>tion1()
+}