Start vectorizing TensorPrimitives (dotnet#91596)

* Start vectorizing TensorPrimitives

Just does two functions to establish the files into which the rest of the implementations can be moved.

Author: stephentoub

src/libraries/System.Numerics.Tensors/src/Resources/Strings.resx

@@ -121,6 +121,6 @@
     <value>Destination is too short.</value>
   </data>
   <data name="Argument_SpansMustHaveSameLength" xml:space="preserve">
-    <value>Length of '{0}' must be same as length of '{1}'.</value>
+    <value>Input span arguments must all have the same length.</value>
   </data>
-</root>
+</root>

src/libraries/System.Numerics.Tensors/src/System.Numerics.Tensors.csproj

@@ -16,6 +16,14 @@
     <Compile Include="System\ThrowHelper.cs" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'">
+    <Compile Include="System\Numerics\Tensors\TensorPrimitives.netstandard.cs" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">
+    <Compile Include="System\Numerics\Tensors\TensorPrimitives.netcore.cs" />
+  </ItemGroup>
+
   <ItemGroup>
     <InternalsVisibleTo Include="System.Numerics.Tensors.Tests" Key="00240000048000009400000006020000002400005253413100040000010001004b86c4cb78549b34bab61a3b1800e23bfeb5b3ec390074041536a7e3cbd97f5f04cf0f857155a8928eaa29ebfd11cfbbad3ba70efea7bda3226c6a8d370a4cd303f714486b6ebc225985a638471e6ef571cc92a4613c00b8fa65d61ccee0cbe5f36330c9a01f4183559f1bef24cc2917c6d913e3a541333a1d05d9bed22b38cb" />
   </ItemGroup>