Suggestion: SAS UI - Unique target-prograde and target-retrograde icons

[Barrackar]

Current behavior: A holdover from KSP1, when you switch to "target" mode the target-prograde and target-retrograde indicators replace the orbital-prograde and orbital-retrograde icon in the user interface.

Suggestion: Create a new icon for target-prograde and target retrograde. Have these two icons appear in the user interface only after something has been selected as a target (i.e. a docking port or celestial body).

Purpose: Avoid confusion between orbital and target icons. For example, Matt Lowne encounters confusion here: https://youtu.be/2E2jScl41w8?t=2245 at around 37:30 when ascending from the Mun.

Suggested implementation: An octagon is not yet used as a symbol - perhaps an orange or white octagon icon can indicate target prograde and the same symbol with bisector hash-marks can indicate target-retrograde. There is a little bit of space between the SAS controls and the time-warp controls so two additional symbols should fit. These can be context dependent and only show on the user interface after a target is selected to avoid clutter.

There are some advantages to displaying redundant information across different modes. A previous UI improvement in KSP1 was to show map information (apogee, perigee) when not in map-view. Showing "target" mode information when in surface/orbital mode is a similar improvement where target-prograde and target-retrograde information would be useful to see while launching back to orbit - and to avoid some current confusion which exists between switching between different modes. The target mode would need to continue to exist because that mode shows additional information like target location and adding all information from target mode into the other modes would create too much UI clutter.