Add test for custom InstaScale controller image support

[astefanutti]

This follows up #120, and adds a test case covering the new controllerImage field of the InstaScale resource.

[astefanutti]

/assign @tedhtchang

/cc @jbusche

[jbusche]

I tested the PR on my OpenShift 4.12.18 cluster, and it worked fine. Can still sub out the InstaScale image when/as needed. When I edit the instascale CR, the CodeFlare operator log catches the change and updates the InstaScale deployment:

2023-06-08T16:31:03-07:00	INFO	Merging	{"diff": "{\"spec\":{\"template\":{\"spec\":{\"$setElementOrder/containers\":[{\"name\":\"instascale\"}],\"containers\":[{\"image\":\"quay.io/project-codeflare/instascale-controller:v0.0.2\",\"name\":\"instascale\"}]}}}}"}
2023-06-08T16:31:03-07:00	INFO	Updating	{"name": "opendatahub/instascale-instascale", "type": "apps/v1, Kind=Deployment"}
2023-06-08T16:31:03-07:00	INFO	Finished applying InstaScale Resources

[jbusche]

LGTM

[openshift-ci]

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[tedhtchang]

thanks @astefanutti /lgtm