SwiftQUIC: PERF: Move CongestionControl state to a common struct

[agnosticdev]

In recent flame graphs for the server we have noticed that findNewlyAckedPackets is a common hotspot when receiving packets for two reasons:

1. The logic in finding the sent path is expensive.
2. The logic in congestionControlPacketsAcked is also expensive due to exclusivity and copies that need to be made every time the enum algorithm alters itself.

For number 1 the sent path can be determined by matching the path identifier on the PacketContainerEntry.

For number 2 we can actually avoid some of the exclusivity and the copying costs by moving the congestion control logic inside a non-copyable struct. Next we can move the common state for all algorithms into a CongestionControlState struct and this is where the common state is now tracked and altered for all algorithms. This essentially shields any copies or writes from being done on QUICPath directly and allows packetsAcked and packetSent to make writes just on the state object and not on QUICPath. This prevents some exclusivity and copies on these two functions.

Net savings of about 430 megacycles:
Top of tree:

2.12 G   4.6%	101.98 M	 Recovery.InnerState.findNewlyAckedPackets(ackFrame:path:now:connection:)	
1.44 G   3.1%	5.20 M  	   Recovery.InnerState.packetAcked(sentPath:sentEntry:connection:)	
163.74 M 0.4%	125.91 M	   Recovery.InnerState.removeSentPacket(_:)
190.84 M 99.2%	1.00 M	       QUICPath.congestionControlPacketsAcked(bytesAcked:sentTime:)	

219.77 M 91.3%	1.00 M	       QUICPath.congestionControlPacketsSent(bytesSent:qlog:)	

With this change:

1.84 G 99.6%	99.03 M	     Recovery.InnerState.findNewlyAckedPackets(ackFrame:path:now:connection:in:) [inlined]	
1.32 G 71.5%	3.32 M	      Recovery.InnerState.packetAcked(sentPath:sentEntry:connection:in:) [inlined]	
58.39 M 3.2%	-	          QUICPath.congestionControlPacketsAcked(bytesAcked:sentTime:) [inlined]	

66.89 M 91.5%	1.20 M	      QUICPath.congestionControlPacketsSent(bytesSent:qlog:) [inlined]	

[agnosticdev]

This change does not change any of the congestion control logic, it just moves the objects around.

[rpaulo]

I would prefer an init where we pass Algorithm and then we do a switch on it.