camera rework and related stuff

yet another attempt at making cameras more usable with some better code but also raw hackery
-view camera when activating a pac_event related to it
-manually view camera via partmenu option, some other part classes have similar activation/preview actions
-better auto-switching between cameras in various cases

PART:SetSmallIcon(str) overrides the tiny event indicator on part icons
used when manually viewing a camera to display an eye showing that this camera is the one being viewed, might be used later

PART:GetReasonsHidden() gives a whole list of reasons as a table of part-indexed strings instead of doing early returns as soon as one reason is found. there are often multiple reasons, a common one is parent hiding
also added parent hiding reason to PART:GetReasonHidden()

use interpolated_multibone's friendlyname in nicename to reflect that we'll refer to interpolated_multibone as interpolator, and added a better nicename showing the nodes

event seen_by_player detects other players' eyeangle raycasts on an adjustable bounding box

new shorthand proxy functions

-nsin makes a normalized sine ranging from 0 to 1, similar to what easy setup needs to do
-nsin2 is the same as nsin but half a pi radians less, so that the cycle's output starts at 0 (assuming 0, the starting value for timeex-based expressions) instead of 0.5
-ncos makes a normalized cosine
-ncos2 is ncos with pi radians less to start output at 0

shortened standard timeex-based fades to replace dual clamp fade-in-fade-out setups. they are normalized (0-1 range).
-ezfade(speed, starttime, endtime) resolves the fade equations by using a desired speed and the extrema. if not enough speed, it might not make the full transition and it'll crossfade before reaching 1
-ezfade_4pt(in_starttime, in_endtime, out_starttime, out_endtime) resolves the fade equations by using the four crossing points

new aliases to save a little bit of text space or perhaps be more meaningful to some:
-if_else = number_operator_alternative
-if_event = if_else_event = event_alternative

event_alternative now defaults the 2nd and 3rd args to 0 and 1. reflecting the event's state, if they are not specified

and server population-related inputs

text part chat support

ChatTyping updates when typing (outgoing networking is stopped when the part is removed and no more text parts requiring ChatTyping are present)

ChatSent reuses say event's existing data

improve hitscan precision

use uints instead of vector, but it'll cost some more as the tradeoff

net_combat: some server stuff moved to serverside

replace D enums with their numbers

apparently they don't exist before pac loads when we need them

implement volume setting, drawable part limiters, NPC friendliness

pac_stopsound works for websound too, unlike console stopsound

clients can choose their own distance limits for sounds, shakes, sunbeams and 2D texts they see
shake also has duration and amplitude limits

new consent cvar for clients to exclude friendly or neutral NPCs from being damaged by hitscan and damage zone

added killicon for pac_bullet_emitter

combat parts reinitialize: from a spawnmenu options button, remotely request the refresh via a net message on multiplayer to make it work on dedicated servers

move combat parts info prints

the requesting of pac combat parts is now silent on join, verbose on the concommand

Remove trailing whitespaces

small correction for shortcut preset