Infered lifetime bounds (RFC 2093)

[matthewjasper]

See rust-lang/rust#44493

• Document existing inferred lifetime bounds in functions and impls
• Document feature. Should this be documented with the existing inferred bounds?
• Make use of in examples

[tlyu]

I think this should have S-waiting-on-stabilization removed; the tracking ticket rust-lang/rust#44493 has closed (notably with the "Adjust documentation" step unchecked). (I'll try to get rustbot to do it, but I might not have permissions.)

@rustbot label -S-waiting-on-stabilization

[tlyu]

I'm willing to work on a PR for this. The "Reference-level explanation" in rust-lang/rfcs#2093 is quite verbose and possibly better suited for implementation documentation. I think I won't copy it directly, but maybe try to summarize it in a way that is accurate enough.

@rustbot claim