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

Tue Feb 4 13:06:24 UTC 2025

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.

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Commit messages:
 - fix & test

Changes: https://git.openjdk.org/jdk/pull/23438/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23438&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349361
  Stats: 414 lines in 8 files changed: 255 ins; 127 del; 32 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