Add standard vertical spacing to some drawers.

[nitz]

A few drawers needed a little breathing room from the controls that followed them, in particular InfoBox and the help box drawn from DrawDefaultPropertyAndHelpBox. Added EditorGUIUtility.standardVerticalSpacing to the heights for those instances. As well, used EditorGUIUtility.standardVerticalSpacing for the height of controls inside a reorderable list, instead of the hardcoded value 4.

The difference in drawing is minimal, sure, but it lets those infoboxes line up in a way that doesn't make them feel like they're crowding the drawer underneath them.

[nitz]

Updated this PR to not conflict with base.