testing: link to fuzzing guide and more details on runtime

[ronaldpetty]

$ go version
go version go1.18beta2 darwin/amd64

The go doc testing and this page https://pkg.go.dev/testing@master#hdr-Fuzzing still are pointing to #48255. They mention:

TODO(#48255): write and link to documentation that will be helpful to users who are unfamiliar with fuzzing.

Some details such as:

• why does it run long (∞) and how to stop
• maybe example quickly shows it 'finding' evil params (the current one ran for 30+ minutes and nothing found)
  • just to show what happens when it does, else you just see endless processing

I was asked to create new ticket (versus comment in #48255).

Looking forward to using it, and thanks for the hard work.

[ianlancetaylor]

CC @golang/fuzzing

[katiehockman]

https://go-review.googlesource.com/c/go/+/383415 fixes the TODO in the testing package 👍

[gopherbot]

Change https://golang.org/cl/383454 mentions this issue: _content/doc/fuzz: describe the nature of a failure

[ronaldpetty]

Thank you @katiehockman . I have solved all my questions after seeing that link (and related ones). Cool feature.