RFR: 8339214: Remove misleading CodeBuilder.loadConstant(Opcode, ConstantDesc)

[Chen Liang]

8339214: Remove misleading CodeBuilder.loadConstant(Opcode, ConstantDesc)

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Commit messages:
 - Improve specs for ConstantInstruction.ofArgument
 - 8339214: Remove misleading CodeBuilder.loadConstant(Opcode, ConstantDesc)

Changes: https://git.openjdk.org/jdk/pull/20779/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20779&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339214
  Stats: 205 lines in 10 files changed: 7 ins; 157 del; 41 mod
  Patch: https://git.openjdk.org/jdk/pull/20779.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20779/head:pull/20779

PR: https://git.openjdk.org/jdk/pull/20779