LibWeb: Switch to new CSS Parser :^)

Change all the places that were including the deprecated parser, to
include the new one instead, and then delete the old parser code.

`ParentNode::query_selector[_all]()` now treat their input as a
comma-separated list of selectors, instead of just one, and return
elements that match any of the selectors in that list. This is according
to these specs:

- querySelector/querySelectorAll:
https://dom.spec.whatwg.org/#ref-for-dom-parentnode-queryselector%E2%91%A0
- selector matching algorithm:
https://www.w3.org/TR/selectors-4/#match-against-tree

Userland/Libraries/LibWeb/HTML/HTMLTableCellElement.cpp

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <LibWeb/CSS/Parser/DeprecatedCSSParser.h>
+#include <LibWeb/CSS/Parser/Parser.h>
 #include <LibWeb/HTML/HTMLTableCellElement.h>
 
 namespace Web::HTML {