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.
We initially just mimicked our old practice of using []string for module
paths here, but the addrs package now gives us a pair of types that better
capture the two different kinds of module addresses we are dealing with:
static addresses (nodes in the configuration tree) and dynamic/instance
addresses (which can represent the situation where multiple instances are
created from a single module call).
This distinction still remains rather artificial since we don't yet have
support for count or for_each on module calls, but this is intended to lay
the foundations for that to be added later, and in the mean time just
gives us some handy helper functions for parsing and formatting these
address types.
This package is intended to contain all the functionality for parsing,
representing, and formatting addresses of objects within Terraform.
It will eventually subsume the responsibilities of both the
InterpolatedVariable and ResourceAddress types in the "terraform" package,
but for the moment is just a set of types for representing these things,
lacking any way to parse or format them. The remaining functionality
will follow in subsequent commits.
