[EuiButton][hasAriaDisabled] cursor: not-allowed not applied

**Describe the bug**
When hovering over a disabled button using `hasAriaDisabled`, the cursor does not change to `not-allowed` because `pointer-events` are set to `none`.

**Expected result**
A disabled button using `hasAriaDisabled` should change the cursor to `not-allowed` on hover. This may require using a different system than `pointer-events: none` to actually disable the button.