Solve Wanted quantified constraints from Givens

This commit ensures we directly solve Wanted quantified constraints from
matching inert Given quantified constraints,instead of going through the
trouble of emitting an implication constraint and processing that.

This is not just an optimisation; it makes our lives easier when
generating RULEs for specialisation.
See Note [Solving Wanted QCs from Given QCs] for details

Fixes #25758