Accessibility: Improve the file upload inputs styling.

Though browsers implement `cursor: pointer` on this kind of controls a bit 
inconsistently, the `pointer` cursor styling makes more clear the button and
label are actionable controls.

Props Ankit K Gupta.
Fixes #35552.


git-svn-id: https://develop.svn.wordpress.org/trunk@38435 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/forms.css

@@ -204,6 +204,7 @@ textarea {
 
 .wp-admin input[type="file"] {
 	padding: 3px 0;
+	cursor: pointer;
 }
 
 label {
@@ -297,6 +298,7 @@ input[type="range"].disabled {
 	background: none;
 	-webkit-box-shadow: none;
 	box-shadow: none;
+	cursor: default;
 }
 
 input[type="checkbox"]:disabled,