Make FhirXml/JsonParser use the POCO-based parsers

[Kasdejong]

We'll leave FhirXmlNode and FhirJsonNode untouched, but in the effort to make the POCO-based stack the default, this should happen asap.

This also helps for unifying the settings.

We should combine ParserSettings and [FhirXml/FhirJson]PocoDeserializerSettings

TODO after PR review:

• Rename BaseFhirJson/XmlPocoDeserializer.cs to BaseFhirJson/XmlParser.cs
• Rename ParserSettings.cs to DeserializerSettings.cs

[ewoutkramer]

Here's an analysis of the current situation, three parsers families:

• FhirXmlParser, FhirJsonParser (old) -> uses the FhirXmlNode/FhirJsonNode parsers
• FhirXmlNode, FhirJsonNode -> ITypedElement based parsers,
• FhirXmlPocoDeserializer/FhirJsonPocoDeserializer -> the newest parsers
• FhirSerializationEngine -> uses last two
• System.Text.Json -> uses the FhirJsonPocoDeserializer via the FhirSerializationEngine

FhirXml/JsonParser(ParserSettings) : BaseFhirParser(inspector,settings)
{
	settings => PocoBuilderSettings
	settings => FhirXmlParsingSettings
	settings => FhirJsonParsingSettings

	FhirJsonNode.Parse(string/JsonReader,FhirJsonParsingSettings)
	FhirXmlNode.Parse(string/XmlReader,FhirXmlParsingSettings)
}

public class ParserSettings
        public bool DisallowXsiAttributesOnRoot { get; set; }
        public bool AllowUnrecognizedEnums { get; set; }
        public bool AcceptUnknownMembers { get; set; }
        public bool PermissiveParsing { get; set; } = true;
        public bool TruncateDateTimeToDate { get; set; } = false;
        public ExceptionNotificationHandler ExceptionHandler { get; set; }

public class PocoBuilderSettings
        public bool AllowUnrecognizedEnums { get; set; } // = false
        public bool IgnoreUnknownMembers { get; set; } // = false
        public bool TruncateDateTimeToDate { get; set; }
        public ExceptionNotificationHandler ExceptionHandler { get; set; }

public class FhirXmlParsingSettings
        public XNamespace[] AllowedExternalNamespaces { get; set; }
        public bool DisallowSchemaLocation { get; set; } // = false;
        public bool PermissiveParsing { get; set; } = true;
        public bool ValidateFhirXhtml { get; set; } // = false;

public class FhirJsonParsingSettings
        public bool PermissiveParsing { get; set; } = true;
        public bool AllowJsonComments { get; set; } // = false;
        public bool ValidateFhirXhtml { get; set; } // = false;

FhirXmlPocoDeserializer(FhirXmlPocoDeserializerSettings)

public class FhirXmlPocoDeserializerSettings
        public IDeserializationValidator? Validator { get; init; } = DataAnnotationDeserialzationValidator.Default;
        public bool ValidateOnFailedParse { get; init; } = false;
        public bool AnnotateResourceParseExceptions { get; init; } = false;

FhirJsonPocoDeserializer(FhirJsonConverterOptions)

public record FhirJsonConverterOptions
    public SerializationFilter? SummaryFilter { get; set; } = null;
    public IDeserializationValidator? Validator { get; init; } = DataAnnotationDeserialzationValidator.Default;
    public bool ValidateOnFailedParse { get; init; } = false;
    public bool AnnotateResourceParseExceptions { get; init; } = false;

[ewoutkramer]

To decide:

• Really obsolete FhirJsonPocoDeserializer?
• FhirJsonParser is now the main class, but actually it should be FhirJsonDeserializer. Worth the name change?
• Also, most of the "legacy" functions we still support are called Parse, while the newer parsers used Deserialize - they are now both there. Obsolete a set?
• DeserializationFailedException is now subclass of StructuralTypeException and FormatException for BW compat reasons. Keep it?
• Try to support JsonReader overloads (=Newtonsoft). Not evident!
• Default changed from "permissive" to "strict". Will that cause problems? Correct for it in DirectorySource and FhirClient?