d3d12: Don't allocate mappable textures

There's not really a reason to directly map textures. Doing so
requires the texture to be allocated in system RAM instead of
video RAM, which means all GPU access to it would be needlessly slow.

Notably, the one texture type that was allocated this way is the
display target texture for the software driver path. Instead, use
pipe_transfer_map to be able to copy the texture to system RAM.

Reviewed-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Part-of: <!8095>
37 jobs for !8095 with d3d12-flush-frontbuffer in 9 minutes and 3 seconds (queued for 3 seconds)
detached
Status Job ID Name Coverage
  Sanity
passed #6480454
sanity

00:00:08

 
  Container
passed #6480459
aarch64 manual
arm_build

00:00:26

passed #6480462
manual
arm_test-base

00:00:13

passed #6480463
windows shell 1809 mesa manual
windows_build_vs2019

00:00:10

passed #6480456
manual
x86_build-base

00:00:16

passed #6480458
manual
x86_test-base

00:00:16

 
  Container 2
passed #6480471
android_build

00:00:13

passed #6480474
arm64_test

00:00:15

passed #6480475
armhf_test

00:00:16

passed #6480468
i386_build

00:00:13

passed #6480464
kernel+rootfs_amd64

00:00:20

passed #6480465
aarch64
kernel+rootfs_arm64

00:01:13

passed #6480466
aarch64
kernel+rootfs_armhf

00:00:18

passed #6480469
ppc64el_build

00:00:15

passed #6480470
s390x_build

00:00:15

passed #6480467
x86_build

00:00:13

passed #6480472
x86_test-gl

00:00:14

passed #6480473
x86_test-vk

00:00:15

 
  Meson X86 64
passed #6480481
meson-clang

00:02:07

passed #6480482
meson-clover

00:02:35

passed #6480478
meson-clover-testing

00:01:13

passed #6480479
meson-gallium

00:02:48

passed #6480480
meson-release

00:01:51

passed #6480476
meson-testing

00:02:05

passed #6480477
meson-testing-asan

00:02:22

passed #6480483
meson-vulkan

00:00:47

 
  Build Misc
passed #6480484
meson-android

00:01:41

passed #6480486
aarch64
meson-arm64

00:01:23

passed #6480487
aarch64
meson-arm64-build-test

00:01:20

passed #6480485
aarch64
meson-armhf

00:02:15

passed #6480490
meson-i386

00:01:53

passed #6480493
meson-mingw32-x86_64

00:00:51

passed #6480492
kvm
meson-ppc64el

00:02:40

passed #6480491
kvm
meson-s390x

00:03:55

passed #6480488
windows docker 1809 mesa
meson-windows-vs2019

00:04:40

passed #6480489
scons-win64

00:03:02

 
  Layered Backends
passed #6480494
windows docker 1809 mesa
test-d3d12-windows

00:03:48