cmd/compile: add more information to the bisect-verbose report
running on cmd/compile/internal/testdata/inlines now shows:
```
--- change set #1 (enabling changes causes failure)
b/b.go:16:6: loop variable i now per-iteration (loop inlined into b/b.go:10)
b/b.go:16:6: loop variable i now per-iteration
./b/b.go:16:6: loop variable b.i now per-iteration (loop inlined into a/a.go:18)
./b/b.go:16:6: loop variable b.i now per-iteration (loop inlined into ./main.go:37)
./b/b.go:16:6: loop variable b.i now per-iteration (loop inlined into ./main.go:38)
---
```
and
```
--- change set #2 (enabling changes causes failure)
./main.go:27:6: loop variable i now per-iteration
./main.go:27:6: loop variable i now per-iteration (loop inlined into ./main.go:35)
---
```
Still unsure about the utility of mentioning the inlined occurrence, but better
than mysteriously repeating the line over and over again.
Change-Id: I357f5d419ab4928fa316f4612eec3b75e7f8ac34
Reviewed-on: https://go-review.googlesource.com/c/go/+/494296
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: David Chase <drchase@google.com>