Replace some gamedata lookups with VScript function bindings

[komashchenko]

Although VScript itself is disabled, its function bindings are still registered and can be accessed through CGameEntitySystem.

This PR replaces several gamedata signatures and offsets with runtime lookups for the following function bindings:

• SetGravity
• SetEntityName
• EmitSoundParams
• SetTeam (ChangeTeam)
• IsPlayerPawn
• IsPlayerController

SetModel could also be resolved this way, but it is currently hooked, so it is intentionally left unchanged. Teleport could potentially be obtained through SetOrigin.

Since the function bindings cannot be resolved before StartupServer is called, the appropriate failure behavior still needs to be determined. For now, lookup failures are reported through Panic, although it may be better to simply use Plat_FatalError instead.

[Vauff]

I would've had concerns about VScript (or even just the CS2 bindings) being cleaned up from the game in the past. But given we're 3 years in to CS2 now, and it's all still there. I don't see any reason why we can't abuse them if they're sticking around, this would've been more stable than relying on signatures/offsets, anyway. Worst case we just revert back to signatures/offsets if Valve does ever go ahead with VScript cleanup.

I would suggest sticking with "VScript" naming to avoid any confusion with cs_script though. I'll do a more thorough review once this is no longer marked as draft.