Prior to the introduction of our "addrs" package, we represented destroy
nodes as a special kind of address string ending in ".destroy" or
".destroy-cbd".
Using references to resolve these dependencies is a strange idea to begin
with, since these are not user-visible addresses, but rather than refactor
that now we instead have these weird pseudo-address types ResourcePhase
and ResourceInstancePhase that correspond go those weird address suffixes,
thus restoring the prior behavior.
In future we should rework this so that destroy node edges are not handled
as references at all, and instead handled as part of
DestroyEdgeTransformer where there's better context for implementing this
logic and it can be maintained and tested in a single place.
This "kitchen sink" commit is mainly focused on supporting "targets" as
a new sub-category of addresses, for use-case like the -target CLI option,
but also includes some other functionality to get closer to replacing
terraform.ResourceAddress and fill out some missing parts for representing
various other address types that are currently represented as strings
in the "terraform" package.
