[Aaronontheweb]

Since the number of possible shards is bounded at startup, we can avoid allocating a string each time we route a message by pre-calculating them in the constructor of the HashCodeMessageExtractor.

This improvement reduces all allocations and reduces latency by 50%.

Before

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19041.1165 (2004/May2020Update/20H1)
AMD Ryzen 7 1700, 1 CPU, 16 logical and 8 physical cores
.NET SDK=5.0.302
  [Host]     : .NET Core 3.1.17 (CoreCLR 4.700.21.31506, CoreFX 4.700.21.31502), X64 RyuJIT
  DefaultJob : .NET Core 3.1.17 (CoreCLR 4.700.21.31506, CoreFX 4.700.21.31502), X64 RyuJIT

Method	Mean	Error	StdDev	Median	Gen 0	Allocated
RouteShardEnvelope	49.05 ns	0.397 ns	0.372 ns	49.02 ns	0.0076	32 B
RouteTypedMessage	45.76 ns	0.952 ns	1.425 ns	44.86 ns	0.0076	32 B

After

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19041.1165 (2004/May2020Update/20H1)
AMD Ryzen 7 1700, 1 CPU, 16 logical and 8 physical cores
.NET SDK=5.0.302
  [Host] : .NET Core 3.1.17 (CoreCLR 4.700.21.31506, CoreFX 4.700.21.31502), X64 RyuJIT

Toolchain=InProcessEmitToolchain  

Method	Mean	Error	StdDev	Allocated
RouteShardEnvelope	24.05 ns	0.096 ns	0.080 ns	-
RouteTypedMessage	28.55 ns	0.171 ns	0.160 ns	-

[Aaronontheweb]

Doesn't make a huge impact in the aggregate benchmarks, however:

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19041.1165 (2004/May2020Update/20H1)
AMD Ryzen 7 1700, 1 CPU, 16 logical and 8 physical cores
.NET SDK=5.0.302
  [Host]     : .NET Core 3.1.17 (CoreCLR 4.700.21.31506, CoreFX 4.700.21.31502), X64 RyuJIT
  Job-MBAVSR : .NET Core 3.1.17 (CoreCLR 4.700.21.31506, CoreFX 4.700.21.31502), X64 RyuJIT

InvocationCount=1  UnrollFactor=1  

Method	StateMode	MsgCount	Mean	Error	StdDev
SingleRequestResponseToLocalEntity	Persistence	10000	115.776 ms	2.2927 ms	4.6834 ms
StreamingToLocalEntity	Persistence	10000	4.884 ms	0.2643 ms	0.7191 ms
SingleRequestResponseToRemoteEntity	Persistence	10000	4,199.020 ms	30.7013 ms	27.2159 ms
StreamingToRemoteEntity	Persistence	10000	505.833 ms	10.0748 ms	14.7676 ms
SingleRequestResponseToLocalEntity	DData	10000	113.480 ms	2.2588 ms	4.7645 ms
StreamingToLocalEntity	DData	10000	4.785 ms	0.3805 ms	1.0918 ms
SingleRequestResponseToRemoteEntity	DData	10000	4,189.848 ms	78.5903 ms	80.7064 ms
StreamingToRemoteEntity	DData	10000	499.897 ms	8.4260 ms	7.4695 ms

[Arkatufus]

LGTM

[Aaronontheweb]

Part of #5203