pkg/fuzzer, executor: collect and substitute known resource values

[a-nogikh]

In the old collide mode (that was replaced in #2788), we used to trigger kernel races of the following form.

1. We execute a call that creates an fd.
2. In parallel, we execute a call that consumes the same (predicted) fd value.

We did it implicitly (by rerunning all calls in parallel without cleaning up the resource value array), now we could implement this in a more explicit form:

• Collect resource values after each prog execution.
• Substitute them in the prog/collide.go mutations.