consolidate DotNetty to use single threadpool

[Aaronontheweb]

part of #4636

[Aaronontheweb]

Before

ProcessorCount:                    16
ClockSpeed:                        0 MHZ
Actor Count:                       32
Messages sent/received per client: 200000  (2e5)
Is Server GC:                      True

Num clients, Total [msg], Msgs/sec, Total [ms]
         1,  200000,      1093,  183115.33
         5, 1000000,    193536,    5167.89
        10, 2000000,    193611,   10330.10
        15, 3000000,    185564,   16167.11
        20, 4000000,    184690,   21658.68
        25, 5000000,    185069,   27017.80
        30, 6000000,    186661,   32144.23

After

ProcessorCount:                    16           
ClockSpeed:                        0 MHZ        
Actor Count:                       32           
Messages sent/received per client: 200000  (2e5)
Is Server GC:                      True         
                                                
Num clients, Total [msg], Msgs/sec, Total [ms]  
         1,  200000,      1466,  136443.40      
         5, 1000000,    183319,    5455.14      
        10, 2000000,    184485,   10841.54      
        15, 3000000,    173371,   17304.35      
        20, 4000000,    177581,   22525.02      
        25, 5000000,    176635,   28307.63      
        30, 6000000,    177138,   33872.07      

Looks like a marginal loss in performance to me, but I'll need to compare this to the idle CPU numbers I've been measuring.

[Aaronontheweb]

This change does not appear to have helped on the idle CPU or performance front. Going to close it.