[Feature] Implement `sol-types` traits in `sol!` without tuples

[DaniPopes]

Component

sol! macro

Describe the feature you would like

Currently we implement all traits by deferring everything to a tuple of the inner types (struct, function arguments and returns, etc.).

This is bad because it:

• duplicates the underlying types
• has lower runtime performance due to needing to clone the types to then just use the tuple by reference
• complicates the API
• limits the number of struct fields, function arguments etc allowed to the max tuple size implemented by the library
• overall, it's just not how you implement procedural macros :smile_cat:

Additional context

No response

[prestwich]

has lower runtime performance due to needing to clone the types to then just use the tuple by reference

this should have been fixed by the Encodable trait being implemented for &(&T, &U, &V) now, no?