[VPlan] Make m_False and m_True matchers stateless. NFC (#221581)
is_zero_int and is_one avoid storage unlike is_specific_int, and allow
the match function to be an inlined isZero/isOne call instead of
APInt::isSameValue.
Improves compile time:
https://llvm-compile-time-tracker.com/compare.php?from=8f7d3ba08f14c3d54b8b407d1758dbd1da01bb38&to=c766163e82ec7a377efc7a26ef1e6db38e0dec1d&stat=instructions:u