clean up ast_java: FieldVariable, Assignment, MethodCall

ast_java doesn't need to know about Type in JavaTypeNamespace.

This commit removes Type in FieldVariable, Assignment, MethodCall

Bug: 110967839
Test: ./runtests.sh
Test: m -j
Change-Id: I496c9785745c415426bd1df0be755e07b7039dd1
4 files changed