RFR: 8051680: (ref) unnecessary process_soft_ref_reconsider

[Albert Mingkun Yang]

This PR consists of 3 commits:

1. Removes the soft-ref reconsideration phase because the soft-ref policy is set before marking (JDK-8269596) and stays the same across the GC cycle. Reconsideration phase should not find anything interesting. That being said, there might be some benefit of using more precise heap usage after marking for soft-ref processing, created JDK-8269798 for exploring that.

2. Removes reloading of `_soft_ref_timestamp_clock` from `java_lang_ref_SoftReference::clock();` because the master clock should only be changed by GC.

3. Rename phase{2,3,4} to phase{1,2,3}.

Test: hotspot_gc

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Commit messages:
 - rename
 - clock
 - phase1

Changes: https://git.openjdk.java.net/jdk/pull/4667/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4667&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8051680
  Stats: 215 lines in 5 files changed: 2 ins; 144 del; 69 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4667.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4667/head:pull/4667

PR: https://git.openjdk.java.net/jdk/pull/4667