RFR: 8342469: Improve API documentation for java.lang.classfile.instruction

[Chen Liang]

Improve the documentation for classfile instructions. Includes links to all opcodes, usage notes for instructions, and other various fixes.

-------------

Commit messages:
 - Typos, long lines
 - Labels
 - Wip instr

Changes: https://git.openjdk.org/jdk/pull/21625/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21625&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342469
  Stats: 1396 lines in 29 files changed: 1064 ins; 12 del; 320 mod
  Patch: https://git.openjdk.org/jdk/pull/21625.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21625/head:pull/21625

PR: https://git.openjdk.org/jdk/pull/21625