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.

libraries/reflect/build.gradle.kts

@@ -34,15 +34,9 @@ pill {
 }
 
 val core = "$rootDir/core"
-val annotationsSrc = "$buildDir/annotations"
 val relocatedCoreSrc = "$buildDir/core-relocated"
 val libsDir = property("libsDir")
 
-sourceSets {
-    "main" {
-        java.srcDir(annotationsSrc)
-    }
-}
 
 val proguardDeps by configurations.creating
 val shadows by configurations.creating {
@@ -55,6 +49,7 @@ dependencies {
     compile(projectDist(":kotlin-stdlib"))
 
     proguardDeps(project(":kotlin-stdlib"))
+    proguardDeps(project(":kotlin-annotations-jvm"))
     proguardDeps(files(firstFromJavaHomeThatExists("jre/lib/rt.jar", "../Classes/classes.jar", jdkHome = File(property("JDK_16") as String))))
 
     shadows(project(":kotlin-reflect-api"))
@@ -69,18 +64,6 @@ dependencies {
     shadows(project(":custom-dependencies:protobuf-lite", configuration = "default"))
 }
 
-val copyAnnotations by task<Sync> {
-    // copy just two missing annotations
-    from("$core/runtime.jvm/src") {
-        include("**/Mutable.java")
-        include("**/ReadOnly.java")
-    }
-    into(annotationsSrc)
-    includeEmptyDirs = false
-}
-
-tasks.getByName("compileJava").dependsOn(copyAnnotations)
-
 class KotlinModuleShadowTransformer(private val logger: Logger) : Transformer {
     @Suppress("ArrayInDataClass")
     private data class Entry(val path: String, val bytes: ByteArray)
@@ -127,7 +110,6 @@ val reflectShadowJar by task<ShadowJar> {
     version = null
     callGroovy("manifestAttributes", manifest, project, "Main", true)
 
-    from(mainSourceSet.output)
     from(project(":core:descriptors.jvm").mainSourceSet.resources) {
         include("META-INF/services/**")
     }