RFR: 8328528: C2 should optimize long-typed parallel iv in an int counted loop [v15]

[Kangcheng Xu]

> Currently, parallel iv optimization only happens in an int counted loop with int-typed parallel iv's. This PR adds support for long-typed iv to be optimized. 
> 
> Additionally, this ticket contributes to the resolution of [JDK-8275913](https://bugs.openjdk.org/browse/JDK-8275913). Meanwhile, I'm working on adding support for parallel IV replacement for long counted loops which will depend on this PR.

Kangcheng Xu has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 34 commits:

 - Merge branch 'openjdk:master' into long-typed-parallel-iv
 - better comment formatting
 - Update loopnode.cpp
   
   update comments and use min_signed_integer()
 - omit source BasicType
 - Merge branch 'openjdk:master' into long-typed-parallel-iv
 - refactor I/L conversion nodes
 - update tests and comments as requested
 - Merge branch 'master' into long-typed-parallel-iv
 - use @run driver and Argument.RANDOM_ONCE
 - Merge branch 'master' into long-typed-parallel-iv
 - ... and 24 more: https://git.openjdk.org/jdk/compare/fb703258...5925761f

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Changes: https://git.openjdk.org/jdk/pull/18489/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18489&range=14
  Stats: 427 lines in 3 files changed: 414 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/18489.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18489/head:pull/18489

PR: https://git.openjdk.org/jdk/pull/18489