RFR: 8341415: Optimize RawBytecodeHelper::next

[Shaojin Wen]

A small optimization to the RawBytecodeHelper::next method
* Remove `len <= 0` once
* merge store opcode and isWide

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Commit messages:
 - merge store opcode & isWide
 - optimize RawBytecodeHelper::next

Changes: https://git.openjdk.org/jdk/pull/21300/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21300&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341415
  Stats: 40 lines in 1 file changed: 9 ins; 14 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/21300.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21300/head:pull/21300

PR: https://git.openjdk.org/jdk/pull/21300