RFR: 8307818: Convert Indify tool to Classfile API

[Oussama Louati]

An indify tool in j.l.i tests (also in vmTestBase) convert some source-code private static methods with MT_ MH_, and INDY_ prefixes into MethodHandle, MethodType, and CallSite constants.
It currently uses ad-hoc code to process class files and intends to migrate to ASM; but since we have the Classfile API, we can migrate to Classfile API instead.

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Commit messages:
 - chore: apply review suggestion
 - chore: apply review suggestion
 - fix: fix test
 - fix: Return access modifiers to their original state
 - fix: Return access modifiers to their original state
 - fix: fixed code
 - fix: fix code
 - remove: remove old implementation of Indify
 - add: add full indify implementation using the CP API
 - fix: got rid of the Bytecode inner class
 - ... and 35 more: https://git.openjdk.org/jdk/compare/4b55fe57...0763be4d

Changes: https://git.openjdk.org/jdk/pull/18841/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18841&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307818
  Stats: 1760 lines in 5 files changed: 415 ins; 795 del; 550 mod
  Patch: https://git.openjdk.org/jdk/pull/18841.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18841/head:pull/18841

PR: https://git.openjdk.org/jdk/pull/18841