Refactored metadata.rs

[Kixiron]

• Removed redundant if lets
• Minimized code duplication
• Split off get fetching of the package table into a separate function
• Overall style and formatting changes

[jyn514]

I think this would be useful if you removed the formatting changes.

[Kixiron]

Ah, turns out using &[Value] doesn't work because it's a closure fed into the function, and therefore its signature has to perfectly match