chore(backport-1.21): Pin charmcraft channel to `3.x/stable` #1184

Job	Run time
Run Tests / Lint Code (pilot)	21s
Run Tests / Integration Test (1.26-strict/stable, integration)	1h 1m 8s
Run Tests / Integration Test (1.26-strict/stable, integration-tls-provider)	57m 12s
Run Tests / Lint Code (gateway)	22s
Run Tests / Integration Test (1.26-strict/stable, integration-tls-secret)	56m 53s
Run Tests / Integration Test (1.29-strict/stable, integration)	59m 25s
Publish Charm / Generate the Charm Matrix	3s
Run Tests / Observability Integration Test (1.25-strict/stable)	54m 12s
Run Tests / Integration Test (1.29-strict/stable, integration-tls-provider)	58m 51s
Run Tests / Observability Integration Test (1.26-strict/stable)	55m 39s
Run Tests / Integration Test (1.29-strict/stable, integration-tls-secret)	55m 33s
Run Tests / Unit Test (pilot)	40s
Run Tests / Unit Test (gateway)	30s
Run Tests / Check libraries (istio-gateway) / Check libraries	3s
Run Tests / Check libraries (istio-gateway) / Lint	8s
Run Tests / Check libraries (istio-pilot) / Check libraries	30s
Run Tests / Check libraries (istio-pilot) / Lint	9s
Publish Charm / Publish Charm (./charms/istio-pilot)	40m 27s
Publish Charm / Publish Charm (./charms/istio-gateway)	15m 43s
	8h 37m 49s

Provide feedback