Add a `--rerun-failed` option that will allow ReFrame to run only the failed test cases in a separate invocation

This request comes from @ZQyou and has been discussed briefly in #1176. 

This option is different from `--max-retries`, which retries the tests in the same run. We want ReFrame to load a result of a previous run (see also #1221) and rerun only the failed test cases.
