RFR: 8339260: Move rarely used constants out of ClassFile [v5]

[Chen Liang]

> Many constants are cluttered in `ClassFile`. However, only a few of them are ever used by regular users, most notably `ACC_` flags and `JAVA_X_VERSION` constants. All other constants are specific and should live in more local locations, such as getters that return these constants.
> 
> This simplification of `ClassFile` constants improves user onramp to the Class-File API.
> 
> Notably, before, if `ClassFile` is static imported, `Opcode` enums must be qualified due to name clashes; this relocation allows `Opcode` enums to be static imported with `ACC_` flags, improving class file writing user experience.

Chen Liang has updated the pull request incrementally with one additional commit since the last revision:

  omission in tests

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20773/files
  - new: https://git.openjdk.org/jdk/pull/20773/files/bbeff620..39c28f39

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20773&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20773&range=03-04

  Stats: 7 lines in 2 files changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/20773.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20773/head:pull/20773

PR: https://git.openjdk.org/jdk/pull/20773