feat: add simple Position/Span From implementations for LineColLocation

[HoloTheDrunk]

What?

Adds From<Position<'_>> and From<Span<'_>> implementations to LineColLocation.

Why?

This will make integrating Pest errors and types into custom error types slightly less verbose.
It's technically possible to create a pest error from a span and then get the LCL from that, but it's an unnecessary overhead.

[NoahTheDuke]

Looks good. Can you write a simple test showing these off?

[HoloTheDrunk]

Never bad to have unit tests, though I can't seem to distill the use case where these implementations are important enough to put it in one given that the issue only crops up when making decently complex wrapping error types.
For example, my use case has errors that look like this

Err(Error::new(
    ErrorKind::Code {
        r#type: CodeError::SignatureMismatch(
            parsed.name,
            parsed.signature,
            loaded.signature(),
        ),
        section: Section::Imports,
    },
    lcl_from_bounds(import.as_span().split()), // This is the part where the lack of a From impl became an issue
))

[NoahTheDuke]

Yeah, I understand how that's hard to distill down for a test. Having a simple unit test works for me, just something to cover the barest case to prevent obvious regressions.