A release or so ago we added `non_exhaustive` to the `Network` enum,
this turned out to make usage of the enum un-ergonomic for downstream
users. After much debate we decided that a way forward was to just
minimize the usage of the enum in the public API by instead use
`AsRef<Params>` so that downstream could define their own network enum
based on the networks they support.
Minimize usage of `Network` by using `AsRef<Params>` as a parameter type
instead. "minimize" because the `Network` still appears in some places.
f6467ac98d