[lworld] RFR: 8349923: Refactor StackMapTable constructor and StackMapReader

[Matias Saavedra Silva]

This patch upstreams a commit from mainline which is needed for the implementation of strict fields.
Originally reviewed-by: coleenp, dholmes

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Commit messages:
 - 8349923: Refactor StackMapTable constructor and StackMapReader

Changes: https://git.openjdk.org/valhalla/pull/1371/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1371&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349923
  Stats: 170 lines in 3 files changed: 61 ins; 18 del; 91 mod
  Patch: https://git.openjdk.org/valhalla/pull/1371.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1371/head:pull/1371

PR: https://git.openjdk.org/valhalla/pull/1371