Stub generation infrastructure (except for metadata generation) for KAPT+K2

This commit includes the basic Java stubs generation infrastructure and
the corresponding tests. The main entry point is called
Kapt4StubGenerator. Calls to it from production code will be added in a
separate commit.

 #KT-51982

plugins/kapt3/kapt3-compiler/testData/converter/strangeIdentifiers.fir.txt

@@ -0,0 +1,62 @@
+@kotlin.Metadata()
+@java.lang.annotation.Retention(value = java.lang.annotation.RetentionPolicy.RUNTIME)
+public abstract @interface Anno {
+
+    public abstract StrangeEnum size();
+
+    public abstract java.lang.String name();
+}
+
+////////////////////
+
+
+@kotlin.Metadata()
+public enum StrangeEnum {
+    /*public static final*/ InvalidFieldName /* = new StrangeEnum() */;
+    @org.jetbrains.annotations.NotNull()
+    private final java.lang.String size = null;
+
+    StrangeEnum(java.lang.String size) {
+    }
+
+    @org.jetbrains.annotations.NotNull()
+    public final java.lang.String getSize() {
+        return null;
+    }
+
+    @org.jetbrains.annotations.NotNull()
+    public static kotlin.enums.EnumEntries<StrangeEnum> getEntries() {
+        return null;
+    }
+}
+
+////////////////////
+
+
+@kotlin.Metadata()
+public final class Test {
+    public final java.lang.String simpleName = null;
+
+    public Test() {
+        super();
+    }
+
+    @org.jetbrains.annotations.NotNull()
+    public final java.lang.String getSimpleName() {
+        return null;
+    }
+
+    public final void simpleFun() {
+    }
+
+    @Anno(name = "Woofwoof", size = StrangeEnum.InvalidFieldName)
+    public final void simpleFun2(@org.jetbrains.annotations.NotNull()
+    java.lang.String a, @org.jetbrains.annotations.NotNull()
+    java.lang.String b) {
+    }
+
+    public final void strangeFun4(@org.jetbrains.annotations.NotNull()
+    java.lang.String a, @org.jetbrains.annotations.NotNull()
+    java.lang.String p1_949560896) {
+    }
+}