internal/fuzz: set timeout for each exec of fuzz target

This change sets a timeout of 10 seconds on each
execution of the fuzz target, both during fuzzing
and during minimization. This is not currently
customizable by the user, but issue #48157 tracks
this work.

Deadlocks will be considered non-recoverable errors,
and as such, will not be minimizable.

Fixes #48591

Change-Id: Ic86e8e9e9a0255e7860f7cbf5654e832785d1cbc
Reviewed-on: https://go-review.googlesource.com/c/go/+/363134


Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>