Remove dependency of serialization on frontend

Move ApplicationExtensionDescriptor and ProjectExtensionDescriptor to
:compiler:util.

compiler/serialization/build.gradle.kts

@@ -5,8 +5,8 @@ plugins {
 
 dependencies {
     compile(project(":compiler:resolution"))
-    compile(project(":compiler:frontend"))
     compile(project(":core:deserialization"))
+    api(project(":compiler:util"))
 
     compileOnly(intellijCoreDep()) { includeJars("intellij-core", rootProject = rootProject) }
 }