Rollup merge of #41838 - z1mvader:fix_fn_args_coerce_closure, r=nikomatsakis

Fixed argument inference for closures when coercing into 'fn'

This fixes https://github.com/rust-lang/rust/issues/41755. The tests  `compile-fail/closure-no-fn.rs` and `compile-fail/issue-40000.rs` were modified. A new test `run-pass/closure_to_fn_coercion-expected-types.rs` was added

r? @nikomatsakis