[code-reflection] RFR: OpBuilder optimizations - part 1.

[Adam Sotona]

This PR include following changes:

- op-building methods isolated from the original code and moved to a synthetic inner class
- fixed boxing in `OpBuilder`
- op-building methods are generated by `BytecodeGenerator` and support wide range of ops
- `CodeModelTranslator` is deleted
- synthetic op-building method overrides significantly reduce overhead (by 60% on `TestBytecode`)

Remaining tasks:

- implement part 2. type-building helper method(s) to reduce the overhead even more
- refactor `OpBuilder` to build `ModuleOp` instead of individual `FuncOp`s (and re-enable `TestCodeBuilder`)
- cleanup `BytecodeGenerator` API

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

Commit messages:
 - nit fixes
 - Merge branch 'code-reflection' into opbuilder-optimizations
 - synthetic helper class generation - work in progress
 - synthetic helper class generation - work in progress
 - synthetic helper class generation - work in progress
 - synthetic helper class generation - work in progress

Changes: https://git.openjdk.org/babylon/pull/679/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=679&range=00
  Stats: 544 lines in 5 files changed: 265 ins; 216 del; 63 mod
  Patch: https://git.openjdk.org/babylon/pull/679.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/679/head:pull/679

PR: https://git.openjdk.org/babylon/pull/679