Switch AllocationOrder to using RegisterClassInfo instead of a BitVector

Switch AllocationOrder to using RegisterClassInfo instead of a BitVector
of reserved registers.

Use RegisterClassInfo in RABasic as well. This slightly changes som
allocation orders because RegisterClassInfo puts CSR aliases last.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132581 91177308-0d34-0410-b5e6-96231b3b80d8