automatically generate desired controller-gen binary

[prashao]

Issue #, if available:
#633

Description of changes:

1. Desired version of controller-gen binary will be automatically generated with 'make build-controller SERVICE=$SERVICE' command
2. Removed kubernetes-sigs/controller-tools from prerequisites as users might try to install controller-gen manually and run into errors mentioned in [Documentation] Dev-docs is not clear about how to install correct controller-gen binary #633 . The Makefile change will anyways install the correct version automatically or indicate the user to install the correct one in case of mismatch as below -

$make build-controller SERVICE=$SERVICE
building ack-generate ... ok.
FATAL: Existing version of controller-gen Version: v0.4.1, required version is v0.4.0.
FATAL: Please uninstall controller-gen and install the required version with scripts/install-controller-gen.sh.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jaypipes]

Thanks @prashao. I wonder if some of the other pre-requisites mentioned in the testing docs (like kind and jq) should have similar PRs...

[prashao]

kind & jq have pretty neat installation instructions so we should be good there.