AVRO-3175 Rust: fix lint/clippy errors

[martin-g]

Fix all linting/clippy errors & warnings.
Add build.sh for Rust that currently supports clean, dist, lint and test targets

Jira

• https://issues.apache.org/jira/browse/AVRO-3175

Tests

Tests' source code has been updated to fix linting/clippy errors and warnings

Commits

Documentation

No public facing API has been modified. No need of documentation changes!

[martin-g]

Cool! GitHub Actions now work too!
Only the Security Audit does not work because it looks for Cargo.toml only in the root folder. There is an open issue: actions-rs/audit-check#116

[martin-g]

Any feedback on the proposed changes ?
//CC @iemejia

[iemejia]

My biggest excuses @martin-g I had checked at this PR like 3 weeks ago and I thought I had approved/merged it, and then I went on holidays. It LGTM I just want to do a tiny ping to @flavray in case he might have some extra comment before merging it.

Thanks (and sorry for the delay, lots of things ongoing these last weeks for me).

[martin-g]

No need to apologies, @iemejia !
Thanks!

[iemejia]

LGTM

[iemejia]

Arghh sorry these have been quite busy days and I somehow missed the notification. Review/Work pace should be back to normal now. Thanks for this one @martin-g