Implement request #64137 (XSLTProcessor::setParameter() should allow both quotes to be used)

This reimplements the parameter handling. Instead of quoting the strings
manually, adding the

Implement request #64137 (XSLTProcessor::setParameter() should allow both quotes to be used)

This reimplements the parameter handling. Instead of quoting the strings
manually, adding them to an array, and passing that as input; use the
libxslt API to pass data verbatim to the processor.
This also simplifies the code a lot.

Closes GH-12331.

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