Fix: WF ICE assumptions on binders

[ssenthilnathan3]

Fixes #160293

-Zassumptions-on-binders ICEs because the solver's well_formed_goals passes terms with resolvable inference variables to unnormalized_obligations, which asserts they're already resolved (unlike other callers).

Resolve inference variables before computing WF obligations.

[rustbot]

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

[rustbot]

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