[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/shadowedJava.kt

@@ -0,0 +1,18 @@
+// WITH_RESOLVE_EXTENSION
+// RESOLVE_EXTENSION_PACKAGE: generated
+// RESOLVE_EXTENSION_SHADOWED: \.hidden\.[a-z]+$
+// UNRESOLVED_REFERENCE
+
+// FILE: TestClass.hidden.java
+package foo;
+
+public class TestClass {
+    public TestClass() {}
+}
+
+// FILE: main.kt
+package foo
+
+fun main() {
+    val x = <caret>TestClass()
+}