lib/xe: Introduce Xe library

Xe, is a new driver for Intel GPUs that supports both integrated
and discrete platforms starting with Tiger Lake (first Intel Xe
Architecture).

Series was split to allow easier review. Library, drm uapi, tests,
tools and other were squashed according to code subject.

This patch introduces library used for Xe tests. As there's not
too trivial to calculate credits for squashed subjects full series
credits are:

Co-developed-by: Matthew Brost
[commits: 90 / lines changed: 12574]
Co-developed-by: Mauro Carvalho Chehab
[commits: 28 / lines changed: 1873]
Co-developed-by: Rodrigo Vivi
[commits: 15 / lines changed: 1317]
Co-developed-by: Jason Ekstrand
[commits: 14 / lines changed: 1418]
Co-developed-by: Francois Dugast
[commits: 8 / lines changed: 1082]
Co-developed-by: Philippe Lecluse
[commits: 6 / lines changed: 560]
Co-developed-by: Zbigniew Kempczyński
[commits: 4 / lines changed: 1091]
Co-developed-by: Matthew Auld
[commits: 3 / lines changed: 35]
Co-developed-by: Niranjana Vishwanathapura
[commits: 2 / lines changed: 66]
Co-developed-by: Maarten Lankhorst
[commits: 2 / lines changed: 774]
Co-developed-by: Ryszard Knop
[commits: 1 / lines changed: 12]
Co-developed-by: Thomas Hellström
[commits: 1 / lines changed: 12]
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
Acked-by: Mauro Carvalho Chehab <mchehab@kernel.org>