[code-reflection] RFR: Code model attribute hard-coded

[Adam Sotona]

This is yet another experimental serialization of code model into a custom method attribute.
It is based on #282 with all the ops tagged and hard-coded and a bit better utilization of constant pool.

Proportional size of the custom attributes vs. text-encoded fields is 21% (16% of the CP entries).

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Commit messages:
 - code cleanup
 - code cleanup
 - Hard-coded CodeModelAttribute work in progress
 - Hard-coded CodeModelAttribute work in progress
 - Hard-coded CodeModelAttribute work in progress
 - Hard-coded CodeModelAttribute work in progress
 - Hard-coded CodeModelAttribute work in progress
 - typo
 - CodeModelAttribute structure cleanup + javadoc work in progress
 - CodeModeAtrtribute documentation work in progress
 - ... and 7 more: https://git.openjdk.org/babylon/compare/9afe3b74...7a94d8db

Changes: https://git.openjdk.org/babylon/pull/290/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=290&range=00
  Stats: 1099 lines in 6 files changed: 1093 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/babylon/pull/290.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/290/head:pull/290

PR: https://git.openjdk.org/babylon/pull/290