-dot-machine-cfg for printing MachineFunction to a dot file

This pass allows a user to dump a MIR function to a dot file
and view it as a graph. It is targeted to provide a similar
functionality as -dot-cfg pass on LLVM-IR. As of now the pass
also support below flags:
-dot-mcfg-only [optional][won't print instructions in the
graph just block name]
-mcfg-dot-filename-prefix [optional][prefix to add to output dot file]
-mcfg-func-name [optional] [specify function name or it's
substring, handy if mir file contains multiple functions and
you need to see graph of just one]

More flags and details can be introduced as per the requirements
in future. This pass is inspired from -dot-cfg IR pass and APIs
are written in almost identical format.

Patch by Yashwant Singh <Yashwant.Singh@amd.com> (yassingh)

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D133709