Clean up trait implementations

[futursolo]

Currently, the traits that's implemented on the structs are kind of messy.
Some traits are not necessary for functionality but are implemented for convenience of other internal logics.

This is usually trivial for normal Rust applications as most of them are not size-sensitive. However, as stylist targets wasm, it needs to be as small as possible.

This issue aims to revisit traits implemented on the types.