Allow skip the whole actions based condition

[theowenyoung]

For my case, some dotfile is only expected to linux system, for now, I have to check every action by where: os.name=="linux"

can we consider some global condition? maybe like:

where: os.name=="linux"
actions:
  - action: command.run
    command: echo

or:

actions:
  - action: skipAll
    where: os.name=="linux"
  - action: command.run
    command: echo 
    

[Lockszmith-GH]

I thought about something like this as well. I think the 'more yaml' based approach would be:
You still group it around the actions.

But I would agree, a solution like that would make the code more dynamic

actions:
  where: os.name=="linux"
  - action: command.run
    command: echo

[rawkode]

I think something like this is pretty easy to add and would also work well with async manifests when we turn them on

where: blah

depends:
- blah

actions:
- blah

I prefer it being outside actions because we already support depends here.

I also like that this could be further enhanced with tags and custom variables at the top level of every manifest

[rawkode]

@icepuma any thoughts on this?

[icepuma]

I'd love to have tags and tags are scriptable with Rhai.

[icepuma]

I've created a draft PR with a possible solution for a more fine grain control over the execution of manifests based on where conditions.

What do you think about @theowenyoung @rawkode?