actions: disable support for deferrals

[liamcervante]

This PR disables deferral support for actions, hopefully temporarily.

Essentially, if an action is deferred it should retroactively mark the resource that triggered it as deferred as well. This leads to dependency problems as other resources could have already executed. The longer term fix for this is to add some kind of post plan step that can properly organise the retroactive deferrals once the outcome of all the planning is known.

For now, the rules are:

1. Actions cannot organically trigger deferrals themselves.
2. Actions can be deferred if a dependency has been deferred.
3. Action invocations can only be deferred if the resource that triggered them is deferred.

There is now logic that returns diagnostics for the above three cases, and ensures that deferrals are disallowed with sensible explanations provided.

[mildwonkey]

oooh thank you, that was my omission - good catch

[mildwonkey]

👍🏻 looks solid to me, thank you!