[GH Actions] Add "Disk Usage" step to Android workflows

Summary:
Just so we can see where we're at with disk usage + monitor things going forward.

Example output:

Depends on D8689

Test Plan: Will land and see what happens.

Reviewers: ashoat, ginsu, jon, tomek, marcin

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D8690