add customized imagepullsecret support in makefile when run deploy

[hchenxa]

cc @yanmxa @clyang82

[hchenxa]

we support the customized imagepullsecret in mcgh CR, since I want to use make deploy to install the mcgh operand on my private cluster, do you think if it's ok to add this? if yes, I can work on this.

[yanmxa]

@hchenxa
I think we have supported the image registry configuration. If there is a difference between our two understandings on this issue, you can give me more information.

[yanmxa]

For the global hub operator, you can specify the IMG to replace the global hub operator image.
And for the global hub operand images, we haven't added the logic to replace the image registry in Makefile, so you can add it if you need.