Select: Merged positioning bugs

[benjamincharity]

• Fix horizontal panel position for checkbox and optgroup selects
• Re-enable panel opening up
• Fix issue where panel opens upwards too far away from select
• Selected option should be vertically centered over select
• Update any tests

Select: Needs more exact horizontal panel positioning

Currently the panel is opened slightly off-centered when dealing with optgroups or checkboxes:

This is likely due to the padding changes for selects with checkboxes.

Select: Panel positioning off when opening up

This seems to be intermittent, but at times when opening up, the panel is much too high

Select: Selected option not fully centered vertically

When a select panel opens, the selected item should be vertically centered.

[benjamincharity]

🎉 This issue has been resolved in version 11.1.16 🎉

The release is available on:

• npm package (@next dist-tag)
• GitHub release

Your semantic-release bot 📦🚀