Add SerializerFactory supertype for Native & JS in FIR serialization plugin.

This supertype is intended to be used with @AssociatedObject on platforms
where reflection possibilities are limited.

plugins/kotlinx-serialization/kotlinx-serialization.k2/build.gradle.kts

@@ -10,6 +10,8 @@ dependencies {
     compileOnly(project(":compiler:fir:tree"))
     compileOnly(project(":compiler:fir:resolve"))
     compileOnly(project(":compiler:fir:entrypoint"))
+    compileOnly(project(":js:js.config"))
+    compileOnly(project(":compiler:cli-common"))
 
     implementation(project(":kotlinx-serialization-compiler-plugin.common"))