[CssSelector] Updated parsers to support namespaces (fix for ClassParser included)

ClassParser was passing improper parameters to `ElementNode`, as well as namespaces simply not being supported in the various parsers. This is a natural extension of #6650, by properly parsing the requested CSS filter if supplied.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | NA
| License       | MIT
| Doc PR        | NA