xmlwriter notsupported methods or arguments

[jakubmisek]

case 1 is

$xmlwriter->startElementNS("s", "root", null);

• .NET XmlWriter does not allow to write prefix without "ns" before ns is specified

case 2 is

$wmlwriter->setIndent(true);

• .NET XmlWriter does not allow changing settings after the XmlWriter is created

Originally posted by @mindfocus in https://github.com/peachpiecompiler/peachpie/issues/755#issuecomment-635067670