Add post_plan_delay option

[jamielinux]

Add a post_plan_delay option so make it possible to configure how long flipper should wait after executing a plan (eg, to prevent quick-fire execution loops).

Also, previously the hardcoded 1s delay came before the Plan executed successfully message, so I've also moved the time.Sleep to after that message.

I made the post_plan_delay default 1s, as the previously hardcoded 1s is like a global default anyway since Hetzner is the only supported provider. (Though maybe there's an argument for the default to be 0. 🤔)

[gzuidhof]

Looks good :) A name proposal is perhaps call it pause instead of delay? (I'm not a native speaker, so you decide what makes more sense!).

[jamielinux]

A name proposal is perhaps call it pause instead of delay?

Both can work :)

Though perhaps pause can imply that something stops until it's explicitly resumed. So I lean delay!