RFR: 8257676: Simplify WeakProcessorPhase [v2]

[Kim Barrett]

> Please review this reimplementation of WeakProcessorPhase.  It is changed to
> a scoped enum at namespace scope, and uses the recently added EnumIterator
> facility to provide iteration, rather than a bespoke iterator class.
> 
> This is a step toward eliminating it entirely.  I've split it out into a
> separate PR to make the review of the follow-up work a bit easier.
> 
> As part of this the file weakProcessorPhases.hpp is renamed to
> weakProcessorPhase.hpp, but git doesn't seem to be recognizing that as a
> rename and (majorly) edit, instead treating it as a remove and add a new
> file.
> 
> Testing: mach5 tier1

Kim Barrett has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into simplify_weak_phase
 - simplify phases and use enum class

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1620/files
  - new: https://git.openjdk.java.net/jdk/pull/1620/files/23fdd553..de6a66fb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1620&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1620&range=00-01

  Stats: 32946 lines in 810 files changed: 24540 ins; 5557 del; 2849 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1620.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1620/head:pull/1620

PR: https://git.openjdk.java.net/jdk/pull/1620