Object pooling on StreamingHub

[mayuki]

This PR makes aggressive use of object pooling in the StreamingHub to reduce memory and object allocation.

Results

Call StreamingHub method / 10 seconds

dotnet run -c Release --no-build -- -u http://localhost:5000 -s StreamingHubComplex

Before

• Allocations
  • 7.34 M objects
  • 853.23 MB
• 1.22 M reqs = Task<ComplexResponse>
• 853.23 / 1.22 = 699.36 MB per 1M reqs
• 7.34 / 1.22 = 6.01 M objs per 1M reqs

After

• Allocations
  • 6.71 M objects
  • 587.56 MB
• 2.22 M reqs = Task<ComplexResponse>
• 587.56 / 2.22 = 264.66 MB per 1M reqs
• 6.71 / 2.22 = 3.02 M objs per 1M reqs

Name	Baseline	PR	Ratio
Memory allocation	699.36 MB	264.66 MB	0.37
Objects allocation	6.01 M	3.02 M	0.5

[!NOTE] At first glance, the rps (requests/sec) values look better in After, but the accuracy of the rps measurement is not guaranteed and is therefore ignored this time.