Auto merge of #115920 - Zoxc:depkind-u16, r=cjgillot

Move `DepKind` to `rustc_query_system` and define it as `u16`

This moves the `DepKind` type to `rustc_query_system` where it's defined with an inner `u16` field. This decouples it from `rustc_middle` and is a step towards letting other crates define dep kinds. It also allows some type parameters to be removed. The `DepKind` trait is replaced with a `Deps` trait. That's used when some operations or information about dep kinds which is unavailable in `rustc_query_system` are still needed.

r? `@cjgillot`