Fixes#5409
I didn't expect this to be such a rabbit hole!
Based on git history, it appears that for "historical reasons"(tm),
setting up the various `state.State` structures for a plan were
_completely different logic_ than a normal `terraform apply`. This meant
that it was skipping things like disabling backups with `-backup="-"`.
This PR unifies loading from a plan to the normal state setup mechanism.
A few tests that were failing prior to this PR were added, no existing
tests were changed.
When working from an existing plan, we weren't setting the PathOut field
for a LocalState. This required adding an outPath argument to the
StateFromPlan function to avoid having to introspect the returned
state.State interface to find the appropriate field.
To test we run a plan first and provide the new plan to apply with
`-state-out` set.
If the cached state file contains a remote type field with upper case
characters, eg 'Consul', it was no longer possible to find the 'consul'
remote plugin.
Mitchell Hashimoto