[CodeGen] Don't check attrs for stack realign (#92564)

shouldRealignStack/canRealignStack are repeatedly called in PEI (through
hasStackRealignment). Checking function attributes is expensive, so
cache this data in the MachineFrameInfo, which had most data already.

This slightly changes the semantics of `MachineFrameInfo::ForcedRealign`
to be also true when the `stackrealign` attribute is set.