Add a form of addPreserved which takes a string argument, to allow passes

Add a form of addPreserved which takes a string argument, to allow passes
to declare that they preserve other passes without needing to pull in
additional header file or library dependencies. Convert MachineFunctionPass
and CodeGenLICM to make use of this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83555 91177308-0d34-0410-b5e6-96231b3b80d8