RFR: 8304139: Add <init>, <clinit>, and main method constants to ClassDescs [v3]

[Chen Liang]

> Add String constants INIT_NAME, CLASS_INIT_NAME, MTD_void for the names and method type of instance and class initializers; add String constant MAIN_NAME and MTD_void_StringArray for the name and method type of main method.
> 
> Update occurrences of <init> and <clinit> in core libraries API specification to refer to these constants. The occurrences in code elsewhere will be converted separately for there are too many.
> 
> See https://mail.openjdk.org/pipermail/classfile-api-dev/2023-March/000233.html

Chen Liang has updated the pull request incrementally with one additional commit since the last revision:

  Remove main related constants, update specification for initialization constants

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13020/files
  - new: https://git.openjdk.org/jdk/pull/13020/files/8dc51b8e..9838e462

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13020&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13020&range=01-02

  Stats: 37 lines in 1 file changed: 0 ins; 30 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/13020.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/13020/head:pull/13020

PR: https://git.openjdk.org/jdk/pull/13020