fix: expose VyperSourceLocation fields

[0xpolarzero]

Expose individual fields in VyperSourceLocation for usage downstream.

This is already the case for the corresponding solc fields:

// crates/artifacts/solc/src/error.rs
#[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct SourceLocation {
    pub file: String,
    pub start: i32,
    pub end: i32,
}

#[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct SecondarySourceLocation {
    pub file: Option<String>,
    pub start: Option<i32>,
    pub end: Option<i32>,
    pub message: Option<String>,
}

[mattsse]

seems reasonable

pending @DaniPopes

[mattsse]

clippy unrelated #334

[0xpolarzero]

Thanks!