RawFilters are not written to request when used on filtered aliases

[PaulEpitomy]

I believe that cause of this is that the AliasAddOperation.FilterDescriptor property is not decorated with [JsonConverter(typeof(CompositeJsonConverter<ReadAsTypeConverter, CustomJsonConverter>))] whereas SearchDescriptor is.

[gmarz]

@PaulEpitomy Indeed this is a bug, thanks for reporting! There may be some other places where this is also an issue, so we'll incorporate this in a larger fix.

[gmarz]

Closed via #1422