RFR: 8325589: C2 SuperWord refactoring: create VLoopAnalyzer with Submodules [v4]

[Emanuel Peter]

> Subtask of https://github.com/openjdk/jdk/pull/16620
> 
> **Goals**:
> - **modularity**: SuperWord is a nasty large class, and it is difficult to know what impacts what.
> - **code reuse**: In the future, we may want to reuse some components of SuperWord in other Vectorizers. For example the post-loop-vectorizer ([JDK-8308994](https://bugs.openjdk.org/browse/JDK-8308994)).
> 
> Hence, I pull some parts out of SuperWord, and put them in a new class `VLoopAnalyzer`, with submodules:
> 
> VLoopAnalyzer
>   VLoopReductions
>   VLoopMemorySlices
>   VLoopBody
>   VLoopTypes
> 
> 
> **Future Work**
> In my draft for https://github.com/openjdk/jdk/pull/16620, I also created a submodule `VLoopDependenceGraph`.
> But that is also a lot of code change.
> I decided to do this in a separate RFE, to keep this patch here reasonably short.
> 
> I also left many functions in `superword.cpp`, even though their classes are in `vectorization.hpp`.
> I think it is easier to review them in their old palces, with minor changes, for now.
> In a future RFE, I can then cleanly copy them, without any changes to them.

Emanuel Peter has updated the pull request incrementally with three additional commits since the last revision:

 - more for Christian
 - Apply suggestions from code review
   
   thanks Christian
   
   Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>
 - VStatus

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17800/files
  - new: https://git.openjdk.org/jdk/pull/17800/files/9a485b0a..ba07a799

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17800&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17800&range=02-03

  Stats: 83 lines in 3 files changed: 32 ins; 12 del; 39 mod
  Patch: https://git.openjdk.org/jdk/pull/17800.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17800/head:pull/17800

PR: https://git.openjdk.org/jdk/pull/17800