Add cloak detection abilities to all ra defenses
(not hbox because it already has cloak detection)
Remove C4 target type from ra vehicles - Tanya was a bit too strong C4ing vehicles
Hind and Longbow were a bit too tanky, so reduced their HP levels from 150 to 100 and 150 to 120 respectively.
Increase prices of yak and hind from $1000 to $1350 (Implicit build time increase as well).
Double projectile speed of AA gun so it misses less often
Remove MustBeDestroyed from cnc support structures
Remove MustBeDestroyed from ra support structures
Merge pull request #6414 from ScottNZ/balance

Some RA balance work