[tests] Refactor AbstractReferenceResolveTest. Part 1

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

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

@@ -1,7 +1,6 @@
 // WITH_RESOLVE_EXTENSION
 // RESOLVE_EXTENSION_PACKAGE: generated
 // RESOLVE_EXTENSION_SHADOWED: \.hidden\.[a-z]+$
-// UNRESOLVED_REFERENCE
 
 // FILE: TestClass.hidden.java
 package foo;