refactor: move snapd client into runner #172

Job	Run time
Define spread matrix	10s
Build concierge	29s
Spread (extra-debs)	50s
Spread (extra-packages-config-file)	1m 15s
Spread (extra-snaps)	59s
Spread (juju-model-defaults)	2m 9s
Spread (overrides-env)	5m 56s
Spread (overrides-priority)	1m 5s
Spread (preset-dev)	6m 13s
Spread (preset-k8s)	2m 52s
Spread (preset-machine)	3m 11s
Spread (preset-microk8s)	4m 34s
Spread (provider-google)	1m 9s
Spread (provider-k8s)	2m 35s
Spread (provider-lxd)	2m 39s
Spread (provider-lxd-init-no-bootstrap)	5m 50s
Spread (provider-microk8s)	3m 39s
Spread (provider-none)	38s
Spread (restore)	7m 44s
	53m 57s

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