Figure out a long term name for CpuMathNative

[maryamariyan]

From @eerhardt on March 26th

from
- internal const string NativePath = @"Microsoft.MachineLearning.CpuMathNative.dll";
to
+ internal const string NativePath = "CpuMathNative";    

Glad this worked, and thanks for filing the CoreCLR issue. As far as I can tell this should work on netcoreapp2.0 and desktop as well, but we should test that since this codepath has undergone a few changes in 2.1. Also we may consider adding something more specific to the name since we won't be able to rely on a fix for dotnet/coreclr#17150. 

[maryamariyan]

From @alexanderkyte on April 13th

I'm a fan of NativeMathIntrinsics or something of the like

[danmoseley]

@eerhardt is it still worth renaming this since it's going away long term? Perhaps we can close this

[eerhardt]

Since this issue was written, we've gotten more native assemblies in ML.NET:

• FactorizationMachineNative
• FastTreeNative
• LdaNative
• SymSgdNative

so really it isn't just about CpuMathNative. It is about having unique native assembly names but we can't have "." in them because of the attached core CLR bug that was fixed in .NET Core 3.0 (but not in 2.1 or 2.2).

[danmoseley]

@shauheen seems to me maybe these names are already reasonable

[abgoswam]

DRI RESPONSE: closing since names sound reasonable enough