Allow custom actions to delete resources.

[crenshaw-dev]

Summary

Actions can currently either update or create resources. We should add the ability to delete resources.

Motivation

This would let an Argo CD admin create an action to delete an individual Pod without granting the ability to delete other resources or theApplication itself.

Proposal

Similar to how update and create are implemented.

The code should verify that the resource is part of the app which it's to be deleted from.

We should also add code to remove or grey out the standard Delete option when a user does not have RBAC access to delete.

[crenshaw-dev]

Would serve as a workaround for this: #3593