RFR: 8335475: ClassBuilder incorrectly calculates max_locals in some cases

[Chen Liang]

Trivial fix for the bug where `StackMapGenerator` is pre-allocating the locals incorrectly, affecting static methods with 0 locals. `StackCounter` was not affected.

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Commit messages:
 - 8335475: ClassBuilder incorrectly calculates max_locals in some cases

Changes: https://git.openjdk.org/jdk/pull/19981/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19981&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335475
  Stats: 32 lines in 2 files changed: 28 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/19981.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19981/head:pull/19981

PR: https://git.openjdk.org/jdk/pull/19981