RFR: 8339401: Optimize ClassFile load and store instructions

[Shaojin Wen]

BytecodeHelpers' loadOpcode and storeOpcode are large methods with code size greater than 325, break it into multiple small methods and call them directly in DirectCodeBuilder

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Commit messages:
 - suggestion from @liach
 - copyright
 - direct call
 - Break up large methods into small ones, so that the code size is less than 325

Changes: https://git.openjdk.org/jdk/pull/20739/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20739&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339401
  Stats: 179 lines in 2 files changed: 107 ins; 0 del; 72 mod
  Patch: https://git.openjdk.org/jdk/pull/20739.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20739/head:pull/20739

PR: https://git.openjdk.org/jdk/pull/20739