RFR: 8324790: ifnode::fold_compares_helper cleanup

[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.

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Commit messages:
 - 8324790: ifnode::fold_compares_helper cleanup

Changes: https://git.openjdk.org/jdk/pull/17601/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17601&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8324790
  Stats: 145 lines in 1 file changed: 47 ins; 58 del; 40 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