Increase the ChangeError len values to u32

[notmandatory]

Description

Fixes issue mentioned in #65 (comment).

I confirmed that if a too long CVC is used then an incorrect len value is returned. After the fix in this PR any CVC less than 2^32 in length will return an error with the actual inputted incorrect CVC length.

Notes to the reviewers

I tested before and after this change with the cli tool and an emulated TAPSIGNER card.

This is a BREAKING CHANGE.

Changelog notice

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 891de46

LGTM!