Apply Namer to Java. (#7194)

* Started applying Namer to Java.

- Java didn't previously have keyword escaping
- Added prefixes and suffixes to the Namer methods
- TODO: migrate previous namer applications to using pre/suffixes
- Java methods / functions are interesting, it's mostly camel case
  except when it involves a struct/enum name. That section is Keep case
- I changed the casing for some internal arguments/variables. This
  violates the "don't change genfiles" rule that I've been using but it
  shouldn't break user code.
- LegacyJavaMethod2 is interesting. Basically, Java has a "mixed" case
  convention where it's camel case, except for the type/variant name
  itself, which is keep case. So a type foo_bar would become getfoo_bar
  instead of getFooBar.

* small fix

* Namer for Namespaces

* removed unused parameter, add const everywhere

* Remove unused argument

* More unused args

* Use mutable reference out parameters

* Made more strings const and inlined const empty strings

* remove do not submit

Co-authored-by: Casper Neo <cneo@google.com>

tests/MyGame/Example/Monster.java

@@ -616,7 +616,7 @@ public final class Monster extends Table {
     if (_o.getVectorOfDoubles() != null) {
       _vectorOfDoubles = createVectorOfDoublesVector(builder, _o.getVectorOfDoubles());
     }
-    int _parent_namespace_test = _o.getParentNamespaceTest() == null ? 0 : MyGame.InParentNamespace.pack(builder, _o.getParentNamespaceTest());
+    int _parentNamespaceTest = _o.getParentNamespaceTest() == null ? 0 : MyGame.InParentNamespace.pack(builder, _o.getParentNamespaceTest());
     int _vectorOfReferrables = 0;
     if (_o.getVectorOfReferrables() != null) {
       int[] __vectorOfReferrables = new int[_o.getVectorOfReferrables().length];
@@ -702,7 +702,7 @@ public final class Monster extends Table {
     addTest5(builder, _test5);
     addVectorOfLongs(builder, _vectorOfLongs);
     addVectorOfDoubles(builder, _vectorOfDoubles);
-    addParentNamespaceTest(builder, _parent_namespace_test);
+    addParentNamespaceTest(builder, _parentNamespaceTest);
     addVectorOfReferrables(builder, _vectorOfReferrables);
     addSingleWeakReference(builder, _o.getSingleWeakReference());
     addVectorOfWeakReferences(builder, _vectorOfWeakReferences);