RFR: 8285364: Use more precise name for ReferenceType::REF_OTHER

[Albert Mingkun Yang]

Simple rename and some comments update.

Test: build

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Commit messages:
 - ref-rename

Changes: https://git.openjdk.java.net/jdk/pull/8332/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8332&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285364
  Stats: 9 lines in 7 files changed: 0 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8332.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8332/head:pull/8332

PR: https://git.openjdk.java.net/jdk/pull/8332