RFR: 8341199: Use ClassFile's new API loadConstant(int)

[Shaojin Wen]

The new API loadConstant(int) can shorten the calling path and can replace ldc when the parameter is of int/Integer type.

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Commit messages:
 - use loadConstant instead of ldc

Changes: https://git.openjdk.org/jdk/pull/21259/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21259&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341199
  Stats: 9 lines in 4 files changed: 0 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/21259.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21259/head:pull/21259

PR: https://git.openjdk.org/jdk/pull/21259