This commit begins the process of modularizing the `wicked` code to
prepare for future additions.  The structure will largely follow the
structure in `net_config` to make the code easy to correlate.  Currently
only the DHCP-related wicked code is split out; more to come.

Adds the corresponding static address modules to both `net_config` and
`wicked`.  The `net_config` module contains the structs that `net.toml`
deserializes into.  The `wicked` module contains the structs that are
serialized into interface configuration files, as well as the code to
convert the `net_config` structs into `wicked*` structs.

This commit adds a `new()` constructor for `WickedInterface`.  This
constructor helps to hide defaults for `WickedControl`, and provides a
base on which to build out the structure (in lieu of a full on builder).
As we add additional struct members, we can add them to this method
rather than to all the callers/users of `WickedInterface`.

This change adds v2 of network config, which supports setting static
addresses and routes.  An additional test macro and associated test
files have also been added to validate the functionality.

This change adds an additional public function to the `lease` module
that allows the user to fetch the path for a given interface's static
lease if it exists.  It renames the original `lease_path` function to
`dhcp_lease_path` to be a bit more descriptive, and moves the shared
functionality to a private function.

This change ensures that when `netdog install` is called when setting up
a static address, the proper lease file is used to write the current IP.
When writing the `resolv.conf` file at this time, we use similar logic
as before, getting settings from DNS config or from the DHCP lease,
since static addresses don't contain DNS info.

This change also unifies the logic of gathering the lease, writing the
resolv.conf and current IP into shared functions.

This commit updates the wicked e2e testing.  It templates the
`net_config.toml` and adds additional config to said file to ensure that
the static address configuration renders properly.  The wicked testing
function has been updated to loop through existing net config versions.

This adds the docs for v2 of network configuration, which supports
adding static addresses and simple routes to an interface.