iris: Enable PIPE_CAP_SURFACE_REINTERPRET_BLOCKS

This makes CompressedTexSubImage from a PBO source do proper GPU
rendering to upload instead of stalling to map the PBO source on
the CPU (then copying it on the CPU).

Thanks Bas Nieuwenhuizen for pointing out that Vulkan includes this
functionality, and to Jason Ekstrand for writing the code I adapted.
Vulkan only supports a single layer, however, and this code tries to
support multiple layers as long as it's miplevel 0.

Improves performance in Sid Meier's Civilization VI:

   Average frame time (ms):         -3.67423% +/- 1.46201% (n=5)
   99th percentile frame time (ms): -5.09910% +/- 3.87874% (n=5)
14 jobs for !783 with iris-pbo-blocks in 9 minutes and 13 seconds (queued for 5 seconds)
latest detached
Status Job ID Name Coverage
  Containers Build
passed #275208
debian

00:00:21

 
  Build+Test
passed #275210
meson-clang

00:08:40

passed #275216
meson-gallium-clover-llvm

00:05:21

passed #275217
meson-gallium-clover-llvm39

00:02:37

passed #275215
meson-gallium-drivers-other

00:04:43

passed #275214
meson-gallium-radeonsi

00:02:59

passed #275218
meson-gallium-st-other

00:04:09

passed #275209
meson-gallium-swr

00:05:30

passed #275213
meson-glvnd

00:03:26

passed #275212
meson-loader-classic-dri

00:03:35

passed #275211
meson-vulkan

00:02:38

passed #275220
scons-llvm

00:03:14

passed #275219
scons-nollvm

00:03:07

passed #275221
scons-swr

00:05:10