RFR: 8339115: Rename TypeKind enum constants to follow code style [v3]

[Chen Liang]

> `TypeKind` enum constants are named in wrong code style; correct them before finalization.
> 
> Also improved `TypeKind` specification to talk about not mentioned `returnType`, `void`, and subword types being erased to int (and how). See the associated CSR too.
> 
> See the HTML output for the changed `JSpec` taglet's `6.5.newarray` rendering: https://cr.openjdk.org/~liach/8339115-typekind/java.base/java/lang/classfile/TypeKind.html
> 
> Note: when reviewing, please use https://cr.openjdk.org/~iris/se/23/spec/draft/java-se-23-draft-spec-37/ instead of JVMS 22 for reference; JVMS 23 has fixed a few ambiguities about subword types being absent from JVM's stack and locals.

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

  space

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20737/files
  - new: https://git.openjdk.org/jdk/pull/20737/files/b7c499fa..41f81fe8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20737&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20737&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20737.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20737/head:pull/20737

PR: https://git.openjdk.org/jdk/pull/20737