Openra: General tunnel issues

[Phrohdoh]

• [x] Actors in tunnels (ground-level, underground, in-air) should not be damaged by DamagedByTerrain #12666
• [ ] We should probably not show the healthbars of damaged non-friendly actors while underground or in ground-level tunnels
• [x] Actors should be (if chosen by the rules author) forced out of tunnels when idle

[Phrohdoh]

Here is a WIP branch to solve these issues but I can't promise it is the right way to do this.

[pchote]

A simpler fix is to disable it using a condition, which is what I did for several other traits. We want to avoid having to add a code dependency from every trait onto the tunnel logic.

[GraionDilach]

Issue 2 is complex, units in tunnels were always shown by health bar in TS and detected enemy subterranean units also revealed themselves via them.

[pchote]

I was planning on repurposing our RA GPS icons (but not the code) for friendly units in tunnels and enemy units detected with sensors. IMO that will be much more polished than showing just the health bars.

[Phrohdoh]

@pchote That would indeed be much easier.
I'll give the DamagedByTerrains the !in-tunnel condition.

[pchote]

Point 3 was solved by #13149, and the second point is covered by #12913.