stdlib: Update the stdlib resource's md5 utils

The commit does the following:

- Moves the md5 functions to their own Python module (this will allow us
to use this elsewhere).
- Add functionality to enable md5 values for directories.
- Adds Pyunit tests for the md5 functionality.

Change-Id: I224d4584ed6c35fac3a75e221b3cb48d863ffa6f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/58849
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
6 files changed