RFR: 8343436: Regression in StackMapGenerator after JDK-8339205

[Adam Sotona]

JDK-8339205 introduced multiple regressions in StackMapGenerator and added a lot of new untested code.

This patch reverts StackMapGenerator to the state before JDK-8339205 and adds one regression test.

Please review.

Thanks,
Adam

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Commit messages:
 - 8343436: Regression in StackMapGenerator after JDK-8339205

Changes: https://git.openjdk.org/jdk/pull/21835/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21835&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343436
  Stats: 354 lines in 2 files changed: 52 ins; 223 del; 79 mod
  Patch: https://git.openjdk.org/jdk/pull/21835.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21835/head:pull/21835

PR: https://git.openjdk.org/jdk/pull/21835