Add isElementSyncer for serverside && add new getElementsSyncedByPlayer

[Xenius97]

Closes #2400

This PR adds isElementSyncer for serverside too (now this function is shared) and adds new getElementsSyncedByPlayer which returns element table synced by player.

Client side:

table getElementsSyncedByPlayer([ filter = "ped,vehicle" ])

Server side:

table getElementsSyncedByPlayer(player, [ filter = "ped,vehicle" ])
bool isElementSyncer(player, element)