An `AddressInner` struct is created when parsing address strings however
address strings do not map 1:1 to `Network` because signet and testnet
use the same bech32 prefix "tb".
We can fix this by inlining the `Payload` variants into `AddressInner`
and adding prefix enums for legacy addresses and a `KnownHrp` for bech32
addresses.
Also enables removing the `AddressEncoding` struct as we can display the
`AddressInner` struct directly. (The `Display` impl is on `AddressInner`
and not directly on address to ignore the `NetworkValidation` wrapper,
may be able to be simplified still further.)
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