tests: Prefix pm_ tests with i915_ and move them to i915/

They are i915-specific, so they belong to the directory.
The (now) infix _pm_ is quite informative and worth keeping.

v2: also prefix .c files

Cc: Petri Latvala <petri.latvala@intel.com>
Cc: Ewelina Musial <ewelina.musial@intel.com>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: Petri Latvala <petri.latvala@intel.com>
20 jobs for master in 3 minutes and 7 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #127937
build:tests-debian-autotools

00:00:53

passed #127934
build:tests-debian-meson

00:00:55

passed #127936
build:tests-debian-meson-arm64

00:00:35

passed #127935
build:tests-debian-meson-armhf

00:00:35

passed #127931
build:tests-fedora

00:01:22

passed #127932
build:tests-fedora-no-libunwind

00:00:45

passed #127933
build:tests-fedora-oldest-meson

00:01:02

 
  Test
passed #127938
test:ninja-test

00:00:25

passed #127939
test:ninja-test-arm64

00:00:55

passed #127940
test:ninja-test-armhf

00:00:30

passed #127941
test:test-list-diff

00:00:18

 
  Deploy
passed #128000
pages

00:00:30

passed pages:deploy

00:00:00

passed #127945
pages

00:00:47

passed #127942
pages

00:00:43

failed pages:deploy

00:00:00

passed pages:deploy

00:00:01

failed pages:deploy

00:00:00

failed pages:deploy

00:00:00

failed pages:deploy

00:00:00