Porting NumberToDouble to managed code. (dotnet/coreclr#20080)

* Porting NumberToDouble to managed code.

* Deleting bcltype/number.cpp and bcltype/number.h

* Fixing NumberToDouble to call Int64BitsToDouble, rather than DoubleToInt64Bits

* Some minor code cleanup in NumberToDouble for better readability.

* Some additional code cleanup in the Number.NumberToDouble.cs code

Signed-off-by: dotnet-bot <dotnet-bot@microsoft.com>

src/System.Private.CoreLib/shared/System.Private.CoreLib.Shared.projitems

@@ -283,6 +283,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\Number.Formatting.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Number.Grisu3.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Number.NumberBuffer.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Number.NumberToDouble.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Number.Parsing.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\NullReferenceException.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\ObjectDisposedException.cs" />

src/System.Private.CoreLib/shared/System/Number.NumberBuffer.cs

@@ -3,22 +3,21 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Runtime.InteropServices;
-using System.Runtime.CompilerServices;
 using Internal.Runtime.CompilerServices;
 
 namespace System
 {
     internal static partial class Number
     {
-        private const int NumberMaxDigits = 50; // needs to == NUMBER_MAXDIGITS in coreclr's src/classlibnative/bcltype/number.h.
+        private const int NumberMaxDigits = 50;
 
         private const double Log10V2 = 0.30102999566398119521373889472449;
 
         // DriftFactor = 1 - Log10V2 - epsilon (a small number account for drift of floating point multiplication)
         private const double DriftFactor = 0.69;
 
         [StructLayout(LayoutKind.Sequential, Pack = 1)]
-        internal unsafe ref struct NumberBuffer // needs to match layout of NUMBER in coreclr's src/classlibnative/bcltype/number.h
+        internal unsafe ref struct NumberBuffer
         {
             public int precision;                       //  0
             public int scale;                           //  4
@@ -35,7 +34,7 @@ internal unsafe ref struct NumberBuffer // needs to match layout of NUMBER in co
             private struct DigitsAndNullTerminator { }
         }
 
-        internal enum NumberBufferKind // needs to match NUMBER_KIND in coreclr's src/classlibnative/bcltype/number.h
+        internal enum NumberBufferKind
         {
             Unknown = 0,
             Integer = 1,