Some of these tests were originally written as part of a custom `run-make`
test, so at that time they weren't able to use the normal compiletest header
directive parser.
Now that they're properly integrated, there's no need for them to use
`compile-flags` to specify the edition, since they can use `edition` instead.
When we extract coverage spans from MIR, we try to "un-expand" them back to
spans that are inside the function's body span.
In cases where that doesn't succeed, the current code just swaps in the entire
body span instead. But that tends to result in coverage spans that are
completely unrelated to the control flow of the affected code, so it's better
to just discard those spans.
