Add more Makefile targets to help. Add test section

[oscr]

What this PR does / why we need it:

Adds more Makefile test targets to the make help target and adds a test section.

make help changes to build section and new test section with the pr:

Build
  build            Build manager binary.
  run              Run a controller from your host.
  docker-build     Build docker image with the manager.
  docker-push      Push docker image with the manager.
  cluster-templates-v1beta1  Generate cluster templates for v1beta1

Test
  test             Run unit tests
  test-coverage    Run test-coverage
  agent-test       Run agent tests
  controller-test  Run controller tests
  webhook-test     Run webhook tests
  test-e2e         Run the end-to-end tests

Build section currently:

Build
  build            Build manager binary.
  run              Run a controller from your host.
  docker-build     Build docker image with the manager.
  docker-push      Push docker image with the manager.
  test-e2e         Run the end-to-end tests
  cluster-templates-v1beta1  Generate cluster templates for v1beta1

[anusha94]

lgtm

[dharmjit]

Thanks! lgtm