fix: keep xml namespace prefixes for tags

[baodrate]

fixes --xml-keep-namespace=true so that element tags keep their namespace prefix. e.g.

<xsi:foo>bar</xsi:foo>

does a roundtrip unchanged (rather than becoming <foo>bar</foo>)

fixes #1730

[baodrate]

Note that when using --xml-raw-token=false this causes any elements with a default namespace (i.e. the xmlns attribute) to become prefixed with the value of xmlns.

This might be out of scope of this PR since --xml-raw-token=false seems to behave incorrectly anyways. e.g.

yq -px -ox --xml-raw-token=false (prior to this PR) already processed:

<foo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <bar xsi:abc="xyz">123</bar>
</foo>

into:

<foo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <bar http://www.w3.org/2001/XMLSchema-instance:abc="xyz">123</bar>
</foo>

which is invalid xml.

I'm not sure how xml-raw-token is supposed to work, so I'm unsure how to fix this. But in any case, it should likely be tracked in a separate issue