Recommit "[ConstraintElim] Enable pass by default."

This reverts commit 695ce48c.

The compile-time regression causing the revert has been fixed. Recommit
the original patch.

Original commit message:

   The pass should help to close a functional gap when it comes to
    reasoning about related conditions in a relatively general way.

    It addresses multiple existing issues (linked below) and the need for a
    more powerful reasoning system was also discussed recently in
    https://discourse.llvm.org/t/rfc-alternative-approach-of-dealing-with-implications-from-comparisons-through-pos-analysis/65601/7

    On AArch64, the new pass performs ~2000 simplifications on
    MultiSource,SPEC2006,SPEC2017 with -O3.

    Compile-time impact:

    NewPM-O3: +0.20%
    NewPM-ReleaseThinLTO: +0.32%
    NewPM-ReleaseLTO-g: +0.28%

    https://llvm-compile-time-tracker.com/compare.php?from=f01a3a893c147c1594b9a3fbd817456b209dabbf&to=577688758ef64fb044215ec3e497ea901bb2db28&stat=instructions:u

    Fixes #49344.
    Fixes #47888.
    Fixes #48253.
    Fixes #49229.
    Fixes #58074.

    Reviewed By: asbirlea

    Differential Revision: https://reviews.llvm.org/D135915