Rename Mozfield / Mozfieldtext to Field and Fieldtext

Split off of Bug 1590894
Rename these to support unprefixed version
Also add alias to keep compatibility

Differential Revision: https://phabricator.services.mozilla.com/D50989

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1592389
gecko-commit: ff9cd9a275796006bc19d706b77b7319fd335d0c
gecko-integration-branch: autoland
gecko-reviewers: emilio

css/css-color/parsing/color-valid.html

@@ -28,6 +28,8 @@
 test_valid_value("color", "rgb(100, 200, 300)", "rgb(100, 200, 255)");
 test_valid_value("color", "rgb(20, 10, 0, -10)", "rgba(20, 10, 0, 0)"); // Not supported by Edge/Safari.
 test_valid_value("color", "rgb(100%, 200%, 300%)", "rgb(255, 255, 255)");
+test_valid_value("color", "field");
+test_valid_value("color", "fieldtext");
 </script>
 </body>
 </html>