Snap

Add APIs to override decoration managers and customize decorations #4929

Job	Run time
arches	1s
mir-libs (amd64)	32m 35s
mir-libs (armhf)	2h 10m 20s
mir-libs (arm64)	2h 8m 34s
snap (canonical/mir-test-tools, amd64)	1h 0m 14s
snap (canonical/mir-test-tools, armhf)	27m 22s
snap (canonical/mir-test-tools, arm64)	35m 18s
snap (canonical/confined-shell-wip, amd64)	30m 39s
snap (canonical/confined-shell-wip, armhf)	25m 2s
snap (canonical/confined-shell-wip, arm64)	27m 20s
snap (canonical/ubuntu-frame, amd64)	37m 38s
snap (canonical/ubuntu-frame, armhf)	25m 0s
snap (canonical/ubuntu-frame, arm64)	28m 57s
snap (Miriway/Miriway, amd64)	19m 11s
snap (Miriway/Miriway, armhf)	23m 6s
snap (Miriway/Miriway, arm64)	24m 57s
	10h 56m 14s

Provide feedback