RFR: 8256814: WeakProcessorPhases may be redundant

[Kim Barrett]

Please review this change which eliminates the WeakProcessorPhase class.

The OopStorageSet class is changed to provide scoped enums for the different
categories: StrongId, WeakId, and Id (for the union of strong and weak).
An accessor is provided for obtaining the storage corresponding to a
category value.

Various other enumerator ranges, array sizes and indices, and iterations are
derived directly from the corresponding OopStorageSet category's enum range.

Iteration over a category of enumerators can be done via EnumIterator.  The
iteration over storage objects makes use of that enum iteration, rather than
having a bespoke implementation.  Some use-cases need iteration of the
enumerators, with storage lookup from the enumerator; other use-cases just
need the storage objects.

Testing:
mach5 tier1-6
Local (linux-x64) hotspot:tier1 with -XX:+UseShenandoahGC

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Commit messages:
 - Remove WeakProcessorPhase, adding scoped enum categories to OopStorageSet.

Changes: https://git.openjdk.java.net/jdk/pull/1862/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1862&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256814
  Stats: 1034 lines in 25 files changed: 400 ins; 465 del; 169 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1862.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1862/head:pull/1862

PR: https://git.openjdk.java.net/jdk/pull/1862