[reduce] Add default error tester to circt-reduce

Nobody has claimed this yet.

As discussed in #1591, it would make sense to have `circt-reduce` provide a few default testers that cover the main things people want to check for in tool output: specific error messages or tool crashes. Something like:

- `--run-script foo.sh`
- `--reduce-error "error: sink ..."`
- `--reduce-crash`

Ideally the `--reduce-error` case would take a regex argument, and multiple `--reduce-error` would imply that all of them must be present in the output. Also, regarding tool options, it would be great to have the tester/tool and its arguments be a positional argument to `circt-reduce`, such that we can do things like:

```
circt-reduce foo.mlir -- firtool --verilog --lower-to-hw --some-magic-flag
```

Possibly even providing a placeholder in the command, like `firtool {} --verilog --lower-to-hw --some-magic-flag` where `{}` would be replaced with the output to be tested.

Start by reading the existing circt-reduce command-line handling and the discussion in #1591. Trace how testers and tool arguments are currently passed, then define support for default error and crash testers, repeated regex conditions, and positional tool arguments or placeholders. Done means these workflows are documented, implemented, and verified by the project's relevant tests.

Written by the indexing model from the issue text.