Clean up inline and external value input highlighting

[rachel-fenichel]

This addresses problems with these blocks and similar ones in RTL:

Previously the inline inputs didn't have a highlight for the top right side (above the tab). There were also a bunch of magic numbers to put things in the right places.

Changes:

• Added top right side highlighting.
• Removed extra magic numbers from the rtl tab highlight.
• The above broke external value inputs, so I also fixed those.
• Removed vertical line below the tab from the tab highlight path.