feat: updates the emoji ID API to be more idiomatic

[AaronFeickert]

Description

Updates the emoji ID public API to be more idiomatic.

Motivation and Context

The emoji ID public API includes functionality to convert to and from types like String and PublicKey, but not idiomatically. This PR updates the API to use From and FromStr trait implementations where possible. It also makes some minor changes to checksum function signatures to avoid unnecessary vector cloning, and improves a test.

How Has This Been Tested?

Existing tests pass.

What process can a PR reviewer use to test or verify this change?

Check that the new API is, in fact, more idiomatic :)

While this doesn't affect consensus or existing databases, this public API change is technically breaking. For example, existing documentation needs to be updated.

[github-actions]

Test Results (CI)

    3 files    120 suites   37m 39s ⏱️
1 277 tests 1 277 ✅ 0 💤 0 ❌
3 823 runs  3 823 ✅ 0 💤 0 ❌

Results for commit 6762f9e.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results (Integration tests)

 2 files  + 2  11 suites  +11   56m 57s ⏱️ + 56m 57s
33 tests +33  32 ✅ +32  0 💤 ±0  1 ❌ +1 
35 runs  +35  32 ✅ +32  0 💤 ±0  3 ❌ +3 

For more details on these failures, see this check.

Results for commit 6762f9e. ± Comparison against base commit 8f1eac6.

♻️ This comment has been updated with latest results.

[sdbondi]

Generally when something is constructed from a string the FromStr trait is more idiomatic.

fn do_something(emoji_id: EmojiId) { ... }

do_something(emoji_str.parse()?);
// equivalent to 
do_something(EmojiId::from_str(emoji_str)?);

It may make sense to implement From<PublicKey> for EmojiId if it isn't already

[SWvheerden]

FromStr is perhaps the better option here and not try_from

https://doc.rust-lang.org/std/str/trait.FromStr.html