Publish allopen compiler plugin separately

- added also 'kotlin-allopen-compiler-plugin-embeddable' to be used with
  'kotlin-compiler-embeddable'
- 'kotlin-maven-allopen' now just depends on
  'kotlin-allopen-compiler-plugin' instead of "embeding" it into itself

^KT-52811 In Progress

plugins/allopen/allopen.embeddable/build.gradle.kts

@@ -0,0 +1,19 @@
+plugins {
+    id("org.jetbrains.kotlin.jvm")
+}
+
+dependencies {
+    embedded(project(":kotlin-allopen-compiler-plugin")) { isTransitive = false }
+}
+
+publish {
+    artifactId = artifactId.replace(".", "-")
+}
+
+runtimeJar(rewriteDefaultJarDepsToShadedCompiler())
+sourcesJarWithSourcesFromEmbedded(
+    project(":kotlin-allopen-compiler-plugin").tasks.named<Jar>("sourcesJar")
+)
+javadocJarWithJavadocFromEmbedded(
+    project(":kotlin-allopen-compiler-plugin").tasks.named<Jar>("javadocJar")
+)