ci: bump juju to 3.6 + charmcraft to 3.x/stable #984

Job	Run time
Run Tests / Bundle Integration	21m 24s
Publish Charm / Generate the Charm Matrix	5s
Run Tests / Individual charm's integration tests (controller)	19m 2s
Run Tests / Lint Code (controller)	22s
Run Tests / Individual charm's integration tests (ui)	16m 30s
Run Tests / Lint Code (ui)	23s
Run Tests / Unit Test (controller)	25s
Run Tests / Unit Test (ui)	26s
Run Tests / Check libraries (jupyter-controller) / Check libraries	34s
Run Tests / Check libraries (jupyter-controller) / Lint	11s
Run Tests / Check libraries (jupyter-ui) / Check libraries	34s
Run Tests / Check libraries (jupyter-ui) / Lint	10s
Run Tests / Terraform (controller) / Apply / Apply Terraform	6m 0s
Run Tests / Terraform (controller) / Check / Check Terraform	5s
Run Tests / Terraform (controller) / Lint / Lint Terraform	15s
Run Tests / Terraform (ui) / Apply / Apply Terraform	5m 31s
Run Tests / Terraform (ui) / Check / Check Terraform	6s
Run Tests / Terraform (ui) / Lint / Lint Terraform	8s
Publish Charm / Publish Charm (./charms/jupyter-ui)	7m 15s
Publish Charm / Publish Charm (./charms/jupyter-controller)	7m 13s
	1h 26m 39s

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