Lint suggestion: Warn if non-trivial work is done inside .expect

[Rufflewind]

Suggestion: It would be useful to issue warnings for cases like .expect(&format!(…)) that, although correct, are often slower than one would expect because the format! occurs regardless of whether the error message is needed.

[oli-obk]

This is a natural extension to the or_fun_call lint

[theotherphil]

I'd like to have a go at this.

Should we suggest unwrap_or_else(|e| panic!(...)) as a replacement?

[oli-obk]

This has been fixed in #2815