Allow exact runtime patch version to be targeted

[govert]

This project file

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0-windows</TargetFramework>
    <RuntimeFrameworkVersion>8.0.6</RuntimeFrameworkVersion>
    <RollForward>Disable</RollForward>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="ExcelDna.AddIn" Version="1.8.0" />
  </ItemGroup>  
</Project>

creates a .runtimeconfig.json file like this:

{
  "runtimeOptions": {
    "tfm": "net8.0",
    "rollForward": "Disable",
    "framework": {
      "name": "Microsoft.NETCore.App",
      "version": "8.0.6"
    },
    "configProperties": {
      "System.Runtime.Serialization.EnableUnsafeBinaryFormatterSerialization": false
    }
  }
}

which I expect should work with this runtime installation

PS C:\Users\GovertvanDrimmelen> dotnet --list-runtimes
[...]
Microsoft.WindowsDesktop.App 8.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

However, when loading the add-in we get this error:

---------------------------
TestExactVersion Add-In - ExcelDna.Host
---------------------------
It was not possible to find a compatible framework version for .NET Desktop Runtime 8.0.0 x64.

You can download .NET Desktop Runtime 8.0.0 x64 from https://dotnet.microsoft.com/en-us/download/dotnet/
---------------------------
OK   
---------------------------

This is because the generated .dna file does not include the patch version

<DnaLibrary RollForward="Disable" Name="TestExactVersion Add-In" RuntimeVersion="v8.0" xmlns="http://schemas.excel-dna.net/addin/2020/07/dnalibrary">

We should extend the version support in the .dna file to include the minor and patch components too.
Taht would allow a user to fix a particular runtime patch version to target.