RFR: 8354871: Replace stack map frame type magics with constants [v2]

[Francesco Andreuzzi]

> In this PR I introduce some constants in `StackMapGenerator`. No change in logic is expected.
> 
> Passes tests in `jdk/classfile`.

Francesco Andreuzzi has updated the pull request incrementally with one additional commit since the last revision:

  Apply suggestions from code review
  
  Co-authored-by: Chen Liang <liach at openjdk.org>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27029/files
  - new: https://git.openjdk.org/jdk/pull/27029/files/0ca1e717..4a9bf431

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27029&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27029&range=00-01

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/27029.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27029/head:pull/27029

PR: https://git.openjdk.org/jdk/pull/27029