Publish 'kotlinx-serialization-compiler-plugin' separately

- Also publish 'kotlinx-serialization-compiler-plugin-embeddable' to be
used with 'kotlin-compiler-embeddable'.
- Now Serialization Maven and Gradle plugins do not embed plugin into
itself, but declare on published one normal dependency.
- 'kotlin-serialization-unshaded' publication is deprecated.

^KT-52811 In Progress

libraries/tools/kotlin-serialization/build.gradle.kts

@@ -14,8 +14,6 @@ dependencies {
 
     commonCompileOnly(project(":kotlin-gradle-plugin"))
     commonCompileOnly(project(":kotlin-compiler-embeddable"))
-
-    embedded(project(":kotlinx-serialization-compiler-plugin")) { isTransitive = false }
 }
 
 gradlePlugin {