Performance: Use Span<T> when parsing

[jaredcnance]

Split is going to allocate at least 2 additional string, and in these cases we should be able to just use Span<T> and allocate only when required.

JsonApiDotNetCore/src/JsonApiDotNetCore/Middleware/RequestMiddleware.cs

Lines 55 to 59 in eb2c309

	private static bool ContainsMediaTypeParameters(string mediaType)
	{
	var mediaTypeArr = mediaType.Split(';');
	return (mediaTypeArr[0] == Constants.ContentType && mediaTypeArr.Length == 2);
	}

JsonApiDotNetCore/src/JsonApiDotNetCore/Services/QueryParser.cs

Lines 97 to 104 in c2cb69f

	var propertyName = key.Split(OPEN_BRACKET, CLOSE_BRACKET)[1];
	var values = value.Split(COMMA);
	foreach (var val in values)
	{
	(var operation, var filterValue) = ParseFilterOperation(val);
	queries.Add(new FilterQuery(propertyName, filterValue, operation));
	}

JsonApiDotNetCore/src/JsonApiDotNetCore/Builders/LinkBuilder.cs

Lines 23 to 37 in 83d4a1d

	private string GetNamespaceFromPath(string path, string entityName)
	{
	var nSpace = string.Empty;
	var segments = path.Split('/');
	for (var i = 1; i < segments.Length; i++)
	{
	if (segments[i].ToLower() == entityName)
	break;
	nSpace += $"/{segments[i]}";
	}
	return nSpace;
	}

JsonApiDotNetCore/src/JsonApiDotNetCore/Internal/Query/RelatedAttrFilterQuery.cs

Lines 18 to 20 in c2cb69f

	var relationshipArray = filterQuery.Attribute.Split('.');
	var relationship = GetRelationship(relationshipArray[0]);

JsonApiDotNetCore/src/JsonApiDotNetCore/Services/JsonApiContext.cs

Line 67 in c2cb69f

var path = context.Request.Path.Value.Split('/');