fix!: change auth_delay to return u8

[notmandatory]

Description

Changes the return value for auth_delay from a usize to a u8. The value will never be more than 15 so a u8 is more appropriate and can be cleanly exposed via FFI.

Notes to the reviewers

This is an API BREAKING change.

I manually tested this change with physical TAPSIGNER, SATSCARD, and SATSCHIP cards via the CLI.

I also removed an unneeded ref return from auth_delay since the type Option<u8> implements the Copy trait.

Changelog notice

• Change return type of auth_delay from a usize to a u8. API BREAKING.

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[reez]

ACK e0afe8c

This is a good change. Clippy failures is all that's blocking merge I think, but merge whenever you're ready