Imply outlives-bounds on lazy type aliases

[fmease]

In the most recent design meeting (2023-11-09), T-lang has decided to move forward with “treating lazy type aliases like structs” with respect to where-clauses. Concretely, this means that we want to check lazy type aliases for well-formedness without implying any bounds other than outlives-bounds. The former has already been implemented, the latter not yet as we don't imply any outlives-bounds at all at the moment.

Opening this issue to properly keep track of this implementation step and to clarify who is the person responsible for the implementation (me as it stands).