Strong aliases for small typenum numbers like P1, P2, ..., P4

[Logarithmus]

Implement some sort of downcasting facility to shorten compile errors. Now P4 is expanded to PInt<UInt<UInt<UInt<UTerm, B1>, B0>, B0>>. It would be nice to have struct Plus4, which would be converted to PInt<...> for computation & then converted back to another strong alias.

Implementation will likely involve fighting orphan rule & using macros.

[Logarithmus]

Using const generic approach like here https://docs.rs/nalgebra/latest/nalgebra/base/dimension/struct.Const.html

[Logarithmus]

Shorten rustc compilation errors for const generics:

• feat: omit suffixes in const generics (e.g. 1_i32) rust-lang/rust#99393

[Logarithmus]

Closed by d0b41ec