Reland "[AArch64][CodeGen] Avoid inverting hot branches during relaxation""

This is a reland of 46d2d759, which was
reverted because of breaking build
https://lab.llvm.org/buildbot/#/builders/21/builds/78779. However, this
buildbot is spuriously broken due to Flang::underscoring.f90 being
nondeterministic.