The version 1.63 satisfies our requirements for MSRV and provides
significant benefits so this commit bumps it. This commit also starts
using weak dependencies.
We are upgrading the MSRV across the whole Rust Bitcoin ecosystem.
Update the README, clippy config file, and CI to use the new MSRV.
Changes to use the new MSRV will be done later.
Add mention of MSRV to `secp256k1-sys`, add unreleased section to both
changelogs.
Martin Habovstiak
Tobin C. Harding
Elichai Turkel