Directory reorganization in xfstests-bld pushed out

["Theodore Ts'o" <tytso@mit.edu>]

I've justed pushed out a change to the xfstests-bld directory which is
especially disruptive for people who are building test appliances
using xfstests-bld.

The directory structure in xfstests-bld reflects its original design
as a hermetic build system for xfstests.  However, these days, its
primary focus is the an test appliance featuring xfstests (but these
days, we also support blktests the Phoronix test suite, etc.) and
drivers to run the test appliance on a variety of environments ---
e.g., kvm-xfstests, gce-xfstests, and android-xfstests.

To make life easier for new users of xfstests-bld, especially who want
to use kvm-xfstests, I've reorganized the directory structure and
moved around files and directories so they are sorted into four
top-level directories:
    
    fstests-bld		The hermetic build system for xfstests
    test-appliance	The test runner infrastructure for xfstests (and blktests
			and Phoronix Test Suite....)
    run-fstests		The test runner command line utilities, namely kvm-xfstests,
			gce-xfstests, etc.
    build-kernel	Utilities to build and configure the Linux kernel in a
			standard way which is easy for the test runners to run.
    
There is a script in fstests-bld/misc/post-reorg-cleanup which may be
helpful in moving the external repos and other files to the proper
places after this reorganization.  Please take a look at it before
running it, and I recommend that you use the --no-action option first.
Since the most developers will only need to run the script once, it
may be a little rough, and it does delete some files and directories.

       	      	   	       	     	 - Ted