Option for automatic target lines display in observer mode

[ubitux]

This issue is a followup of #17311.

The feature request can be summarized with: a toggle option to display target lines automatically on player event, optionally without the need for making a selection first:

I9gk827.mp4

This is basically a PoC obtained with sed 's/WhenSelected//g' -i OpenRA.Mods.Common/Traits/Render/DrawLineToTarget.cs (not sure if still working with bleed though).

After a discussion with @dragunoff, it appears a simple way of having this feature in cheaply would be to add them to a status bar with other information (such a unit stances for a given selection). It would include a toggle to toggle target line on and off, and selection only.

Rationale for this feature:

• It gives immediate attention feedback on what the players are focused on (useful for casting)
• It shows the amount of micro involved by the players (useful for educational purpose while analyzing replays)
• No need to make constant selections and keep pressing shift