frontend: custom Actions: merge link and edit panes

Current behaviour

The custom Actions table has separate buttons for each Action for editing and linking:

The link button controls linked variables that are tracked for changes to trigger the Action, as well as the global rate limit on how often the Action can be called, whereas the pencil button allows editing the Actions definition.

As these are both configuration of the action, it's cumbersome to have separate buttons for them, and unintuitive that the minimum trigger interval is defined in the linking section.

Expected or desired behaviour

The buttons should be merged together into a combined editing/configuration menu, withs sections for the relevant functionality split.

Per prior discussion the sections could be handled as tabs, or be collapsible sections within a single pane.

Prerequisites

• I have checked to make sure that a similar request has not already been filed or fixed.