Rollup merge of #107348 - lcnr:project-solve-new, r=compiler-errors

small refactor to new projection code

extract `eq_term_and_make_canonical_response` into a helper function which also is another guarantee that the expected term does not influence candidate selection for projections.

also change `evaluate_all(vec![single_goal])` to use `evaluate_goal`.

the second commit now also adds a `debug_assert!` to `evaluate_goal`.

Author: GuillaumeGomez