rust/base64: upgrade crate to latest

rust/base64: upgrade crate to latest

base64 crate is updated to the latest version 0.22.1. This came with
several API changes which are applied to the code. The old calls have
been replaced with the newer calls.

This was done following the availability of better fns to directly
decode into slices/vectors as needed and also that previous version was
too old.
Along with this change, update the Cargo.lock.in to reflect all changes
in the package versions.

Task 7219