Catalog: Deprecate custom image param from cluster tasks

Changing image reference in any cluster task makes it unsupportable so those params should not be exposed.

Customers who need to run an operator-provided cluster task with their own custom image need to create a copy of a task.

Acceptance criteria:

• buildah task doesn't expose "BUILDER_IMAGE" param
• git-clone task doesn't expose "gitInitImage" param
• kn task doesn't expose "kn-image" param
• kn-apply task doesn't expose "KN_IMAGE" param
• maven task doesn't expose "MAVEN_IMAGE" param
• s2i-* tasks don't expose "BUILDER_IMAGE" param
• tkn task doesn't expose "TKN_IMAGE" param