[Serialization] Harden the compiler tag check on swiftmodules
[Serialization] Harden the compiler tag check on swiftmodules

When two different serialization formats share a version number but are
different enough, it can defeat the check to restrict loading
swiftmodules built by the same compiler. Add a backup check in case the
REVISION block is unseen, for swiftmodules only not swiftdoc or
sourceinfo.

rdar://93188070

roambotics/swift,JGiola/swift,apple/swift,benlangmuir/swift,benlangmuir/swift,JGiola/swift,benlangmuir/swift,glessard/swift,ahoppen/swift,roambotics/swift,ahoppen/swift,JGiola/swift,glessard/swift,glessard/swift,ahoppen/swift,apple/swift,roambotics/swift,apple/swift,benlangmuir/swift,roambotics/swift,benlangmuir/swift,JGiola/swift,JGiola/swift,apple/swift,ahoppen/swift,glessard/swift,glessard/swift,roambotics/swift,roambotics/swift,ahoppen/swift,glessard/swift,benlangmuir/swift,ahoppen/swift,apple/swift,JGiola/swift,apple/swift