feat(rust): Replace base64-url with base64

[Mr-Leshiy]

Description

Replace base64-url which is simply just a wrapper over base64 crate https://github.com/magiclen/base64-url/blob/7bcd29e6b1c21bc4b2592d40d9b493ab4ff3fad4/Cargo.toml#L16.
Simplify our dependency tree.

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 302/302}$ | ${\color{red}Fail: 0/302}$ |

[stevenj]

This is not a necessary change. Not prioritized.
This change would then require a release and bumping other crates.
Not approved.

[no30bit]

Could be opinionated, but I'd re-export URL_SAFE_NO_PAD from catalyst-types as DEFAULT_BASE64 to eliminate the choice among alphabets in every instance of the decoding/encoding logic.

[stevenj]

Could be opinionated, but I'd re-export URL_SAFE_NO_PAD from catalyst-types as DEFAULT_BASE64 to eliminate the choice among alphabets in every instance of the decoding/encoding logic.

I agree, using this raw is a bit ugly. So if we re-export it, we can make it look nicer, and instead of doing this:

            base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(pk.as_bytes())

We could still say use base64_url as exported from catalyst_types with these as well.
Reduces our dependencies, and also means anything which imports catalyst_types (which is everything) can just use our rexeported version, they don't also need base64 as a dependency directly.