RFR: 8349361: C2: RShiftL should support all applicable transformations that RShiftI does [v10]

[Roland Westrelin]

> This change refactors `RShiftI`/`RshiftL` `Ideal`, `Identity` and
> `Value` because the `int` and `long` versions are very similar and so
> there's no logic duplication. In the process, support for some extra
> transformations is added to `RShiftL`. I also added some new test
> cases.

Roland Westrelin 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 17 additional commits since the last revision:

 - review
 - Merge branch 'master' into JDK-8349361
 - review
 - review
 - review
 - Merge branch 'master' into JDK-8349361
 - Update src/hotspot/share/opto/mulnode.cpp
   
   Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
 - Update src/hotspot/share/opto/mulnode.cpp
   
   Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
 - review
 - Update src/hotspot/share/opto/mulnode.hpp
   
   Co-authored-by: Jasmine Karthikeyan <25208576+jaskarth at users.noreply.github.com>
 - ... and 7 more: https://git.openjdk.org/jdk/compare/c4fb8d3d...d3b1cf08

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23438/files
  - new: https://git.openjdk.org/jdk/pull/23438/files/5b05d222..d3b1cf08

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23438&range=09
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23438&range=08-09

  Stats: 5943 lines in 194 files changed: 3935 ins; 1352 del; 656 mod
  Patch: https://git.openjdk.org/jdk/pull/23438.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23438/head:pull/23438

PR: https://git.openjdk.org/jdk/pull/23438