RFR: 8270282: Semantically rename reference processing subphases

[Albert Mingkun Yang]

Simple rename of phase{2,3,4} to something with semantic meaning.

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Commit messages:
 - phase1-rename

Changes: https://git.openjdk.java.net/jdk/pull/4752/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4752&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8270282
  Stats: 85 lines in 4 files changed: 0 ins; 1 del; 84 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4752.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4752/head:pull/4752

PR: https://git.openjdk.java.net/jdk/pull/4752