chore: convert all relative imports to absolute imports

[agriyakhetarpal]

Description

This is a small PR that does some cleanup I wanted to do for a while:

• Converted all relative imports to absolute imports
• Added a rule against this: https://docs.astral.sh/ruff/rules/relative-imports/

Relative imports are not bad, it's just that absolute imports are nicer, at least to me :)

[ryanking13]

Thanks! I often use relative imports just to not repeat the package name everywhere, but I don't have much preference, so I am okay with this change.

[agriyakhetarpal]

That's a valid reason to use them, too!