arm: looprestoration: Simplify code by allowing writing up to 8 pixels past the end of rows

This corresponds to what the x86 assembly does right now.

This allows removing a fair bit of code, and allows marking the stores
as aligned. (Previously, the writes of the narrow slice temp buffer
were unaligned.)
35 jobs for arm-looprestoration-overwrite in 17 minutes and 46 seconds (queued for 41 seconds)
Status Job ID Name Coverage
  Style
passed #517557
amd64 docker
style-check

00:00:08

passed #517558
amd64 docker
x86inc-check

00:00:08

 
  Build
passed #517569
amd64 docker
build-android-aarch64

00:00:17

passed #517568
amd64 docker
build-android-armv7

00:00:17

passed #517559
amd64 avx2 docker
build-debian

00:00:51

passed #517570
aarch64 docker
build-debian-aarch64

00:00:27

passed #517571
aarch64 docker
build-debian-aarch64-clang-5

00:00:26

passed #517574
armv7 docker
build-debian-armv7

00:00:51

passed #517575
armv7 docker
build-debian-armv7-clang-5

00:00:44

passed #517562
amd64 docker
build-debian-examples

00:00:28

passed #517577
ppc64le docker
build-debian-ppc64le

00:01:23

passed #517560
amd64 docker
build-debian-static

00:01:35

passed #517573
aarch64 docker
build-debian-werror

00:00:19

passed #517561
amd64 docker
build-debian32

00:00:31

passed #517572
macos
build-macos

00:01:22

passed #517578
amd64 docker
build-pages

00:00:13

passed #517576
amd64 docker
build-ubuntu-snap

00:00:28

passed #517566
amd64 docker
build-win-arm32

00:00:18

passed #517567
amd64 docker
build-win-arm64

00:00:18

passed #517563
amd64 docker
build-win32

00:00:43

passed #517564
amd64 docker
build-win32-unaligned-stack

00:00:33

passed #517565
amd64 docker
build-win64

00:00:52

 
  Test
passed #517579
amd64 docker
test-debian

00:01:57

97.893%
passed #517588
aarch64 docker
test-debian-aarch64

00:00:37

passed #517590
armv7 docker
test-debian-armv7-clang-5

00:00:55

passed #517583
amd64 docker
test-debian-asan

00:02:13

passed #517580
avx2 amd64 docker
test-debian-asm

00:01:12

passed #517584
amd64 docker
test-debian-msan

00:01:21

passed #517589
ppc64le docker
test-debian-ppc64le

00:01:59

passed #517586
amd64 docker
test-debian-tsan

00:01:47

passed #517585
amd64 docker
test-debian-ubsan

00:01:40

passed #517582
amd64 avx2 docker
test-debian-unaligned-stack

00:00:46

passed #517581
avx2 amd64 docker
test-debian32-asm

00:01:15

passed #517609
docker avx2 amd64
test-win64

00:02:15

failed #517587
amd64 avx2 docker
test-win64

00:01:28