Buddy code cleanup

- Get rid of buddyCnt, self-nullptr checks, and redundant playermap loops in chat handlers
- Add helper function to find available buddy slot
- Reorganize a bit

src/PlayerManager.cpp

@@ -293,9 +293,6 @@ void PlayerManager::enterPlayer(CNSocket* sock, CNPacketData* data) {
     // TODO: check if serialkey exists, if it doesn't send sP_FE2CL_REP_PC_ENTER_FAIL
     Player plr = CNSharedData::getPlayer(enter->iEnterSerialKey);
 
-    plr.buddyCnt = 0;
-    std::cout << "Buddy Count: " << plr.buddyCnt << std::endl;
-
     plr.groupCnt = 1;
     plr.iIDGroup = plr.groupIDs[0] = plr.iID;