Add make target for custom-deploy

[ChristianZaccaria]

Issue link

Closes #152

The changes here are similar to what is done in this PR for MCAD

What changes have been made

• The custom-deploy make target can be used for building and pushing a custom image of InstaScale and deploying it on your K8s cluster for development.
• Added documentation to Readme.

Note: using the name custom-deploy for the make target as there is already an existing easy way of deploying InstaScale (latest) to your K8s cluster. This make target focuses on the custom image deployments.

Verification steps

Example: make custom-deploy ENGINE=<podman or docker> IMG=quay.io/<username>/instascale:<image tag>

Checks

• [x] I've made sure the tests are passing.
• Testing Strategy
  • [x] Manual tests

[ChristianZaccaria]

I have run the make command on an OSD cluster and can confirm that an instascale-controller-manager deployment and pod are created where I can view Instascale logs. I applied an appwrapper and can see that instascale picks it up as expected also. Just one small comment regarding the command in make file. Otherwise it looks good.

@Fiona-Waters Brilliant, thanks for testing it out!

[ChristianZaccaria]

@anishasthana Hi again, could we get this merged as well please? It's from last sprint [InstaScale]

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: anishasthana, VanillaSpoon

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