[code-reflection] RFR: Remove Java prefix from Java ops

[Paul Sandoz]

Remove Java prefix from Java ops as in `Java.IfOp` rather than `Java.JavaIfOp`.

Rename op factory methods that use an `_` prefix (because the name is a Java keyword) to use a `_` postfix (like the ClassFile API).

-------------

Commit messages:
 - HAT updates
 - Update examples
 - Remove Java prefix from Java ops.

Changes: https://git.openjdk.org/babylon/pull/476/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=476&range=00
  Stats: 548 lines in 44 files changed: 2 ins; 7 del; 539 mod
  Patch: https://git.openjdk.org/babylon/pull/476.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/476/head:pull/476

PR: https://git.openjdk.org/babylon/pull/476