There are two canonical orderings for sealed items: preference
order and encoding order. Removing the `Ord` instances means
that a user can't accidentally choose the wrong ordering;
these orderings are replaced by explicit `preference_order`
and `encoding_order` comparison functions.
This renames the `FromReceivers` trait to `UnifiedEncoding` and makes
its public methods (as well as the private to_bytes method) function in
terms of network values rather than explicit HRP arguments. It also adds
high-level encoding and decoding methods that handle conversion to and
from the Bech32m-encoded transport format for all supported types, and
then delegates to these from locations that previously used lower-level
utilities.