feat: Cluster-scoped Rollouts support

[jparsai]

What does this PR do / why we need it:
This PR is to add support for cluster scoped Rollouts. Currently Rollouts controller can reconcile CR created in same namespace, this PR has changes which would allow Rollouts controller to reconcile CR created in other namespaces as well.
There are few limitations for creating Cluster scoped Rollouts controller, please check original issue created for this feature.

Have you updated the necessary documentation?

• Documentation update is required by this PR, and has been updated.

Which issue(s) this PR fixes:
Fixes #?
#20

How to test changes / Special notes to the reviewer:

1. Create RolloutManager CR and change scope to namespace or cluster using Spec.NamespaceScoped field of RolloutManager.
2. Create Rollouts CR if RolloutManager is cluster scoped and it should be reconciled.
3. Try combinations of cluster and namespace scoped Rollouts controller to confirm it works as expected and doesn't allow unsupported scenarios.

[jgwest]

Looks great, thanks Jayendra! See below for requested changes, but it's just minor stuff that I noticed while going the code (some of which was carried over from the original code)

In addition:

• We should add ClusterRole/Binding to SetupWithManager, otherwise we won't be notified about changes to these resources

• There are a few places where we are verifying that resources exist (for example, that a Deployment exists of name DefaultArgoRolloutsResourceName), but not the actual contents of those resource (for example, that the Deployment has the expected values inside)

  • I saw a couple spots where this was true, and it would be good to add some quick additional tests to verify resource contents:
    • In validateArgoRolloutManagerResources for E2E tests
    • argorollouts_controller_test.go (I know this came from the original test code, but can likely reuse the same code used for E2E tests here too)

[jparsai]

Addressed all review comments, PTAL.

[jgwest]

@jparsai did you miss pushing a commit, by chance? I started re-reviewing by checking the first two comments , and it seems like both are still present in the code.

[jparsai]

Yes @jgwest the first comment about duplicate import I had fixed but it seems when I copied some code from another file to rollout_test.go it was added again because of auto import in VSCode.

About 2nd comment I removed the error Type and using only one type "Reconciled", but Reason has to have multiple values.
Type=Reconciled | Status = true | Reason=Success | Message = ""
Type=Reconciled | Status = false | Reason=ErrorOccurred | Message = "Some error message"

I removed duplicate import, PTAL.

[jgwest]

@jparsai Perfect, it's likely I misread reason and type, thanks for double checking!

[jparsai]

@jgwest PR is ready for review now, PTAL.

[jgwest]

Looks great! All that's is just some miscellaneous small items I noticed while reviewing,