uefi: Make TimeError more descriptive

[andre-braga]

When returning a TimeError, it'd be helpful to specify to the user which field is invalid so that it can be handled accordingly, or at least communicated. This change does this by reimplementing TimeError as an enum instead of a struct, allowing for specification and more verbose error display.

Checklist

• Sensible git history (for example, squash "typo" or "fix" commits). See the Rewriting History guide for help.
• Update the changelog (if necessary)

[andre-braga]

Is there a reason for no top level enums in uefi-raw? If not I can add it to xtask, or just place this into uefi instead.

[andre-braga]

Ah, I see the relevant section in api_guidelines now, I'll go about changing things

[phip1611]

LGTM apart from #1211 (review)

[andre-braga]

I instead went with the struct method, allowing one to specify multiple errors.

Is this err == TimeError::default() idea that I've used idiomatic?

[phip1611]

I instead went with the struct method, allowing one to specify multiple errors.

Is this err == TimeError::default() idea that I've used idiomatic?

We're almost there. Just add one more comment and we are good to go