Add workflow for building runner image #8

Job	Run time
Build runner image for containers	25m 0s
Integration test / Get runner image / Get runner image	4s
Integration test / Build and push charm	4m 32s
Integration test / Build image / Get images	3s
Integration test / Build rock / Get rocks	6s
Integration test / Build image / Build image	0s
Integration test / Build rock / Build rock	0s
Integration test / Get rocks or Docker images	1s
Integration test / Integration tests / Integration tests (test_charm_fork_repo)	33m 34s
Integration test / Integration tests / Integration tests (test_charm_no_runner)	23m 36s
Integration test / Integration tests / Integration tests (test_charm_scheduled_events)	33m 2s
Integration test / Integration tests / Integration tests (test_charm_one_runner)	22m 26s
Integration test / Integration tests / Integration tests (test_charm_metrics)	28m 11s
Integration test / Integration tests / Integration tests (test_self_hosted_runner)	27m 54s
Integration test / Integration tests / Integration tests (test_charm_with_proxy)	20m 34s
Integration test / Required Integration Test Status Checks	1s
Build runner image for virtual machine	0s
	3h 39m 4s

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