RFR: 8285364: Remove REF_ enum for java.lang.ref.Reference [v10]

[Albert Mingkun Yang]

> Simple rename and some comments update.
> 
> Test: build

Albert Mingkun Yang has updated the pull request incrementally with four additional commits since the last revision:

 - arg rename
 - default arg
 - revert
 - fix-build

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/8332/files
  - new: https://git.openjdk.org/jdk/pull/8332/files/f7a5f1e6..1e4c71ad

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=8332&range=09
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=8332&range=08-09

  Stats: 74 lines in 6 files changed: 33 ins; 29 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/8332.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/8332/head:pull/8332

PR: https://git.openjdk.org/jdk/pull/8332