The version 1.63 satisfies our requirements for MSRV and provides
significant benefits so this commit bumps it. This commit also starts
using some advantages of the new MSRV, namely namespaced features, weak
dependencies and the ability to use trait bounds in `const` context.
This however does not yet migrade the `rand-std` feature because that
requires a release of `secp256k1` with the same kind of change - bumping
MSRV to 1.63 and removing `rand-std` in favor of weak dependency.
We intend on splitting the address types and logic out into a separate
crate. In preparation for doing so, and so that we can grab the name on
crates.io, add an empty crate `bitcoin-addresses`.
Tie it in to the CI infrastructure.
Martin Habovstiak
Tobin C. Harding