RFR: 8324790: ifnode::fold_compares_helper cleanup [v3]

[Joshua Cao]

> I hope my assumptions  in `filtered_int_type` are correct here:
> 
> * we assert that `if_proj` is an `IfTrue` or `IfFalse`, so it is safe to assume `if_proj->_in` is an  `IfNode`
> * the 1'th input of a CmpNode is a BoolNode
> * Tthe 1'th input of an IfNode is **not always a BoolNode**, it can be a constant. We need to leave this check in.
> 
> We also remove a some of the if-checks in `compare_folds_cleanup` which seem unnecessary.
> 
> Passes tier1 locally.

Joshua Cao 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 five additional commits since the last revision:

 - sanity check that hi and lo are not nullptr
 - Merge branch 'master' into compare_folds_cleanup
 - Undo changes in filtered_int_type()
 - Merge branch 'master' into compare_folds_cleanup
 - 8324790: ifnode::fold_compares_helper cleanup

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17601/files
  - new: https://git.openjdk.org/jdk/pull/17601/files/19e1fa81..341b5006

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17601&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17601&range=01-02

  Stats: 10715 lines in 328 files changed: 6180 ins; 2313 del; 2222 mod
  Patch: https://git.openjdk.org/jdk/pull/17601.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17601/head:pull/17601

PR: https://git.openjdk.org/jdk/pull/17601