[ruby/prism] Begin splitting the Java artifact into components

* The Loader API lives under java/api.
* The current native endpoint for the Prism shared library lives
  under java/native.
* The WASM build and binding lives under java/wasm.

The libraries will be released together but can be developed and
snapshotted independently. Users that copy the source from the
previous java/ will want to grab both java/api/src/main/java and
java/native/src/main/java contents.

ruby/prism@03358d5bcf

Author: headius

prism/templates/template.rb

@@ -688,9 +688,9 @@ def locals
       "javascript/src/deserialize.js",
       "javascript/src/nodes.js",
       "javascript/src/visitor.js",
-      "java/org/ruby_lang/prism/Loader.java",
-      "java/org/ruby_lang/prism/Nodes.java",
-      "java/org/ruby_lang/prism/AbstractNodeVisitor.java",
+      "java/api/src/main/java/org/ruby_lang/prism/Loader.java",
+      "java/api/src/main/java/org/ruby_lang/prism/Nodes.java",
+      "java/api/src/main/java/org/ruby_lang/prism/AbstractNodeVisitor.java",
       "lib/prism/compiler.rb",
       "lib/prism/dispatcher.rb",
       "lib/prism/dot_visitor.rb",