RFR: 8325589: C2 SuperWord refactoring: create VLoopAnalyzer with Submodules [v3]

[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 with a new target base due to a merge or a rebase. The pull request now contains eight commits:

 - manual merge
 - move _loop_or_ctrl from ResouceArena, bc ResourceMark in SuperWord::dependence_graph
 - remove some comments
 - VLoopTypes
 - VLoopBody
 - VLoopMemorySlices
 - VLoopReductions
 - 8325589

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Changes: https://git.openjdk.org/jdk/pull/17800/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17800&range=02
  Stats: 818 lines in 7 files changed: 439 ins; 204 del; 175 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