Support multiple attempts on only a single rule, not all rules

[nh13]

I want to have a single rule retried but all other rules fail after one retry. This is currently not possible for --restart-times I believe.

For the single rule I retry, I also want to retry it based on some lambda. Of course, I could I set --restart-times to a large number, and then throw an exception when the rule has attempted enough times.

The use case would be to implement a memory-doubling strategy for a rule. So the definition of a rule may say it starts at 2GB, doubles each time up to 128GB. Those values may be variable depending on the user config.

Another use case would be to have some custom logic in the "do-retry" lambda that examines the previous output etc. I could of course have that stuffed into the start of a "run" section.

[kpj]

See also #367.

[kpj]

@nh13: What do you think about the new rule-specific retries directive added in #1649?