Implement Pkl binary renderer and parser (#1203)

Implements a binary renderer for Pkl values, which is a lossless capturing of Pkl data.

This follows the pkl binary format that is already used with `pkl server` calls, and is
made available as a Java API and also an in-language API.

Also, introduces a binary parser into the corresponding `PObject` types in Java.

pkl-commons-test/pkl-commons-test.gradle.kts

@@ -28,6 +28,7 @@ dependencies {
   api(libs.junitParams)
   api(projects.pklCommons) // for convenience
   implementation(libs.assertj)
+  implementation(libs.msgpack)
 }
 
 /**