vfio: selftests: Split run.sh into separate scripts

vfio: selftests: Split run.sh into separate scripts

Split run.sh into separate scripts (setup.sh, run.sh, cleanup.sh) to
enable multi-device testing, and prepare for VFIO selftests
automatically detecting which devices to use for testing by storing
device metadata on the filesystem.

 - setup.sh takes one or more BDFs as arguments and sets up each device.
   Metadata about each device is stored on the filesystem in the
   directory:

	   ${TMPDIR:-/tmp}/vfio-selftests-devices

   Within this directory is a directory for each BDF, and then files in
   those directories that cleanup.sh uses to cleanup the device.

 - run.sh runs a selftest by passing it the BDFs of all set up devices.

 - cleanup.sh takes zero or more BDFs as arguments and cleans up each
   device. If no BDFs are provided, it cleans up all devices.

This split enables multi-device testing by allowing multiple BDFs to be
set up and passed into tests:

For example:

  $ tools/testing/selftests/vfio/scripts/setup.sh <BDF1> <BDF2>
  $ tools/testing/selftests/vfio/scripts/setup.sh <BDF3>
  $ tools/testing/selftests/vfio/scripts/run.sh echo
  <BDF1> <BDF2> <BDF3>
  $ tools/testing/selftests/vfio/scripts/cleanup.sh

In the future, VFIO selftests can automatically detect set up devices by
inspecting ${TMPDIR:-/tmp}/vfio-selftests-devices. This will avoid the
need for the run.sh script.

Reviewed-by: Alex Mastro <amastro@fb.com>
Tested-by: Alex Mastro <amastro@fb.com>
Reviewed-by: Raghavendra Rao Ananta <rananta@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20251126231733.3302983-3-dmatlack@google.com
Signed-off-by: Alex Williamson <alex@shazbot.org>