Replace ReadOnly/Mutable usages in the compiler

Replace ones from org.jetbrains.kotlin package with new annotations from kotlin.annotations.jvm.
No need to copy them to compile kotlin-reflect anymore.
Then simplify reflect project more: no sources — no need to pack its direct output.

core/descriptors.jvm/build.gradle.kts

@@ -7,6 +7,7 @@ jvmTarget = "1.6"
 javaHome = rootProject.extra["JDK_16"] as String
 
 dependencies {
+    compile(project(":kotlin-annotations-jvm"))
     compile(project(":core:descriptors"))
     compile(project(":core:deserialization"))
     compile(project(":core:metadata.jvm"))

core/descriptors.jvm/src/org/jetbrains/kotlin/load/java/JavaClassFinder.java

@@ -16,9 +16,9 @@
 
 package org.jetbrains.kotlin.load.java;
 
+import kotlin.annotations.jvm.ReadOnly;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.jetbrains.annotations.ReadOnly;
 import org.jetbrains.kotlin.load.java.structure.JavaClass;
 import org.jetbrains.kotlin.load.java.structure.JavaPackage;
 import org.jetbrains.kotlin.name.ClassId;