runtime(java): Tidy up the syntax file

runtime(java): Tidy up the syntax file

- Prefix all global variables with "g:".
- Add spaces around each variable assignment operator.
- Remove extraneous whitespace characters.
- Remove a spurious _serializable_ Java keyword (since v1.1,
  java.io.Serializable and java.io.Externalizable interfaces
  provide an API for object serialization; see vim-6-0j).
- Normalise the syntax definition argument order by making
  _contained_ the first argument of each such definition.
- Normalise the argument tabulation for highlighting group
  definitions.

Reference:
https://web.archive.org/web/20010821025330/java.sun.com/docs/books/jls/first_edition/html/1.1Update.html

related: #15399

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>