Unify height of PC3 buttons, TextFields, and Comboboxes

Now all of them have a base height of units.gridUnit. Combined with the standard 6px margins it works out to make all of these controls a uniform 30px tall with the default Noto Sans 10 font. If the font is changed or the size is increased, even to absurd levels, all of them scale evenly.

Nice and consistent heights at the default 10pt Noto Sans font:

All of them scale evenly; here seen with 15pt Noto Sans:

Size looks good when buttons are made larger than normal:

Pin button looks normal-sized again:

ToolButtons in list items have correct proportions:

cc @teams/vdg