feat: Add `promote-to-stable` action #1

Job	Run time
🖥 Get snap architectures	3s
🖥 Get snap architectures	3s
🖥 Get snap architectures	3s
🚢 Release to latest/candidate (amd64)	27m 35s
🚢 Release to latest/candidate (amd64)	27m 35s
🚢 Release to latest/candidate (amd64)	27m 35s
🚢 Release to latest/candidate (arm64)	4m 9s
🚢 Release to latest/candidate (arm64)	57m 2s
🚢 Release to latest/candidate (arm64)	57m 2s
🚢 Release to latest/candidate (ppc64el)	4m 11s
🚢 Release to latest/candidate (ppc64el)	4m 25s
🚢 Release to latest/candidate (ppc64el)	45m 35s
🚢 Release to latest/candidate (s390x)	41m 58s
🚢 Release to latest/candidate (s390x)	41m 58s
🚢 Release to latest/candidate (s390x)	41m 58s
📣 Create call for testing	0s
📣 Create call for testing	0s
📣 Create call for testing	20s
	6h 21m 32s

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