[Mono.Options] Fix test and add suite to CI (#4963)

[Mono.Options] Fix test and add suite to CI (#4963)

* [Mono.Options] Fix test and add suite to CI

We missed running Mono.Options tests on CI so we didn't catch
this error which was introduced with: https://github.com/mono/mono/pull/4719

```
CSC     [net_4_x-darwin] net_4_x_Mono.Options_test.dll
Test/Mono.Options/CommandSetTest.cs(231,16): error CS7036: There is no argument given that corresponds to the required formal parameter 'error' of 'CommandSet.CommandSet(string, TextWriter, TextWriter, Converter<string, string>)'
```

* [Mono.Options] Stop hardcoding \n to fix tests on Windows