Improve workflow execution UX

This is continuation of .

We are talking here about Execute Workflow menu which is part of:
1. Deployments widget - action button on the right side of the table
2. Deployment Action Buttons widget - Execute Workflow button on the left side
3. Spire Manager widget - Execute Workflow button

Ideas to consider:
1. Make Execution Workflow menu two-layered - when grouping workflows by originating plugin is applied, then it'd prefer to show workflows using two-layered menu instead of accordion-like solution.
2. Make Install and Uninstall (maybe consider another workflows, too?) more visible for the user - within we changed visibility in Deployments widget action menu, we should make similar change in the other places.
3. Make the available options context-aware (e.g. uninstall can be disabled if there are no installed nodes).