Allow whitespace around path expressions in xpath

[simonwuelker]

Previously servo would allow whitespace in between components of an xpath expression, but not around it.

Testing: New web platform tests start to pass
Part of #34527

[yezhizhen]

This change itself doesn't allow whitespace at end of path expression.

Or it already did elsewhere?

[simonwuelker]

This change itself doesn't allow whitespace at end of path expression.

Or it already did elsewhere?

ws accepts whitespace both before and after the supplied parser function:

servo/components/script/xpath/parser.rs

Lines 915 to 921 in 629b7db

	fn ws<'a, F, O, E>(inner: F) -> impl Parser<&'a str, Output = O, Error = E>
	where
	E: NomParseError<&'a str>,
	F: Parser<&'a str, Output = O, Error = E>,
	{
	delimited(multispace0, inner, multispace0)
	}

(I'm not super happy with the structure of the parser, but thats a bigger issue...)

Accepting whitespace after the expression is also verified by the web platform tests:

servo/tests/wpt/tests/domxpath/lexical-structure.html

Lines 13 to 14 in 629b7db

	parse(' \'a"bc\' ');
	parse(' "a\'bc" ');