Handle higher-ranked trait bounds in suggest_impl_fn_for_fn_ptr_ret.

[TirushOne]

Adresses #159481.
Builds on #159594.

Summery

Handle higher-ranked trait bounds in suggest_impl_fn_for_fn_ptr_ret. If the fn type had higher-ranked trait bounds, the suggested impl Fn replacement will now have the same higher-ranked trait bounds.

Changed how rustc_hir_pretty handles lifetimes, it know only prints explicit lifetimes, i.e. lifetimes that exist in the source code. Previously it would print implicit lifetimes as '_. This change was made to make code suggestions less verbose and make prints of the HIR match the source code more closely. Without this change, suggest_impl_fn_for_fn_ptr_ret would suggest replacing fn(&()) -> &() with impl Fn(&'_ ()) -> &'_ (), now it will suggest the more intuitive impl Fn(&()) -> &().

[rustbot]

r? @jackh726

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