RFR: 8349923: Refactor StackMapTable constructor and StackMapReader

[Matias Saavedra Silva]

This patch refactors the `StackMapReader` to clean up the `StackMapTable` constructor. The `StackMapReader` class is extended to hold more fields used for verification purposes and allows for a simpler StackMapTable constructor. Additionally, in preparation for further changes to verification, the `_frame_count` may not be equal to the value reported by the classfile. Verified with tier 1-5 tests

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Commit messages:
 - Refactor StackMapTable constructor and StackMapReader

Changes: https://git.openjdk.org/jdk/pull/23645/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23645&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349923
  Stats: 158 lines in 3 files changed: 65 ins; 15 del; 78 mod
  Patch: https://git.openjdk.org/jdk/pull/23645.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23645/head:pull/23645

PR: https://git.openjdk.org/jdk/pull/23645