[fix] Redis connection counter didn't work properly

[rennokki]

For the Redis replicator, each time a new connection is opened or closed, it will increment a value in the database.

Until now, the connection counts were kept in the channel manager and it caused the multi-node deployments to fail to display the right amount of connections and even track them (for example, keeping track the max amount of connections for each app) because the connection counts were hold into each node's memory.

The Redis database will keep a value for the opened connections for each app, instead of letting each server declare the connections number for each app.

[codecov-commenter]

Codecov Report

Merging #497 into 2.x will decrease coverage by 16.11%.
The diff coverage is 15.72%.

@@              Coverage Diff              @@
##                2.x     #497       +/-   ##
=============================================
- Coverage     78.13%   62.01%   -16.12%     
- Complexity        0      355      +355     
=============================================
  Files            55       56        +1     
  Lines          1372     1477      +105     
=============================================
- Hits           1072      916      -156     
- Misses          300      561      +261     

Impacted Files	Coverage Δ	Complexity Δ
src/PubSub/Drivers/RedisClient.php	0.00% <0.00%> (-67.28%)	31.00 <5.00> (+31.00)	⬇️
src/Statistics/Logger/RedisStatisticsLogger.php	0.00% <0.00%> (-64.78%)	17.00 <0.00> (+17.00)	⬇️
...s/Channels/ChannelManagers/RedisChannelManager.php	0.00% <0.00%> (ø)	2.00 <2.00> (?)
src/PubSub/Drivers/LocalClient.php	86.48% <50.00%> (-10.07%)	15.00 <4.00> (+15.00)	⬇️
src/WebSockets/WebSocketHandler.php	82.05% <52.63%> (-9.89%)	22.00 <4.00> (+22.00)	⬇️
src/Statistics/Logger/MemoryStatisticsLogger.php	91.89% <100.00%> (ø)	12.00 <0.00> (+12.00)
...s/Channels/ChannelManagers/ArrayChannelManager.php	97.29% <100.00%> (+0.15%)	13.00 <2.00> (+13.00)
src/WebSocketsServiceProvider.php	98.03% <100.00%> (+0.08%)	4.00 <0.00> (+4.00)
src/Console/RestartWebSocketServer.php	80.00% <0.00%> (-20.00%)	1.00% <0.00%> (+1.00%)	⬇️
... and 4 more

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[rennokki]

Just managed to turn the then()s into blocking I/O for the unit testing 🎉 The PR got testing for functionality (with 2 incomplete tests tho; might look after it soon).