Extract `SmallMap` into an utility crate

[jedel1043]

Implementation: https://github.com/boa-dev/boa/blob/main/core/engine/src/small_map/mod.rs

[countradooku]

Can i work on that?

[jedel1043]

@radudiaconu0 Of course! I realized the link to the existing implementation was wrong, so I updated it.

You should be able to basically do the same as https://github.com/boa-dev/boa/tree/main/utils/tag_ptr

[countradooku]

thanks