No scrollbar in Select when menu has dividers (#6804)

Co-authored-by: Brandon Cheng <[email protected]>

packages/select/src/components/select/_select.scss

@@ -3,26 +3,33 @@
 
 @import "../../common/variables";
 
+$select-padding: $pt-grid-size * 0.5;
+
 .#{$ns}-select-popover {
  .#{$ns}-popover-content {
  // use padding on container rather than margin on input group
  // because top margin leaves some empty space with no background color.
- padding: $pt-grid-size * 0.5;
+ padding: $select-padding;
  }
 
  .#{$ns}-input-group {
  margin-bottom: 0;
  }
 
  .#{$ns}-menu {
+ // offset the padding added by the select componenent so menu can remain full width with padding on either side
+ // this is important so menu dividers can be full width, and so that menu items can have padding to the left and right
+ // for menu items
+ margin-left: -$select-padding;
+ margin-right: -$select-padding;
  max-height: $select-popover-max-height;
  max-width: $select-popover-max-width;
  overflow: auto;
- padding: 0;
+ padding: 0 $select-padding;
 
  &:not(:first-child) {
  // adjust padding to account for that on .#{$ns}-popover-content above
- padding-top: $pt-grid-size * 0.5;
+ padding-top: $select-padding;
  }
  }