Move non-x86 tests to GHA

[nulano]

For #5028 (comment).
Companion to python-pillow/docker-images#98.
Includes #5091.

Move tests of arm64v8, ppc64le, s390x from Travis CI to GHA Docker tests using aptman/qus.

Other changes:

• (Mark new test failures on non-x86 as xfail #5091) Add xfail to libtiff tests that are failing on big-endian (see also Big-endian test failures on IBM Z #4213 (comment)).
• (Mark new test failures on non-x86 as xfail #5091) Add xfail to test_libimagequant_quantize failing on ppc64le (not sure why).
• FreeType 2.6 is no longer tested, remove FreeType<2.7 metrics from tests (see also Deprecate old FreeType? #5075).

The new tests will fail until the new images get pushed, see run in my branch for now: https://github.com/nulano/Pillow/actions/runs/416245841

Speed comparison (approximate)

Architecture	Travis CI	GHA / Create Docker image	GHA / Test in Docker image	GHA Total
arm64	7 min	15 min 50 sec	8 min 15 sec (1.18x Travis)	24 min 5 sec
ppc64le	4 min 20 sec	16 min (*)	9 min 15 sec (2.15x Travis)	25 min 15 sec (*)
s390x	2 min 15 sec	14 min (*)	11 min 45 sec (5.22x Travis)	25 min 45 sec (*)

*: The ppc64le and s390x image builds currently fail a bit early due to new test failures, the install time will be slightly longer.

The total is a bit faster than I saw in #5028 (comment) mostly because it installs WebP from apt-get instead of compiling locally. More importantly, only the test times should matter, which are in line with cache-miss Windows tests and slightly slower than macOS tests.

Dependency versions:

Travis CI (removed):

--- PIL CORE support ok, compiled for 8.1.0.dev0
*** TKINTER support not installed
--- FREETYPE2 support ok, loaded 2.6.1
--- LITTLECMS2 support ok, compiled for 2.6
--- WEBP support ok, loaded 1.1.0
--- WEBP Transparency support ok
--- WEBPMUX support ok
--- WEBP Animation support ok
--- JPEG support ok, compiled for libjpeg-turbo 1.4.2
--- OPENJPEG (JPEG2000) support ok, loaded 2.1.2
--- ZLIB (PNG/ZIP) support ok, loaded 1.2.8
*** LIBTIFF support not installed
*** RAQM (Bidirectional Text) support not installed
--- LIBIMAGEQUANT (Quantization method) support ok, loaded 2.13.1
--- XCB (X protocol) support ok

Ubuntu Focal in Docker (python-pillow/docker-images#98):

--- PIL CORE support ok, compiled for 8.1.0.dev0
--- TKINTER support ok
--- FREETYPE2 support ok, loaded 2.10.1
--- LITTLECMS2 support ok, loaded 2.9
--- WEBP support ok, loaded 0.6.1
--- WEBP Transparency support ok
--- WEBPMUX support ok
--- WEBP Animation support ok
--- JPEG support ok, compiled for libjpeg-turbo 2.0.3
--- OPENJPEG (JPEG2000) support ok, loaded 2.3.1
--- ZLIB (PNG/ZIP) support ok, loaded 1.2.11
--- LIBTIFF support ok, loaded 4.1.0
--- RAQM (Bidirectional Text) support ok, loaded 0.7.0
--- LIBIMAGEQUANT (Quantization method) support ok, loaded 2.12.0
--- XCB (X protocol) support ok

[radarhere]

(I see Raqm 0.7.0 in tests in this repo, but Raqm 0.7.1 in python-pillow/docker-images#98. Is it being replaced somewhere? Everything else matches exactly.)

Pillow uses the images from Docker that have been pushed by docker-images stable jobs. So when the next Pillow release occurs, docker-images stable jobs will have an updated version of Pillow that specifies 0.7.1 in 'depends/install_raqm.sh' and then it will be updated to 0.7.1 here.

[nulano]

Oh right, I was looking at the latest jobs, not stable.

[hugovk]

Thank you!

Similar to my comment at python-pillow/docker-images#98 (comment), these timings aren't too bad (especially if Travis is essentially dead!), and it's worth trying it out.

Let's also put these slower ones first in the matrix here as well.

[nulano]

I reordered the images and opened #5091 with just the xfail part of this.