[Microsoft.Sbom.Targets] Generate SbomGenerationPackageVersion with Nerdbank.GitVersioning

[KalleOlaviNiemitalo]

The version number generated by Nerdbank.GitVersioning 3.6.133 does not automatically propagate into the SBOM file generated by Microsoft.Sbom.Targets 2.2.8, which instead defaults to version 1.0.0. I put this thing in my project to fix that:

  <Target Name="SetSbomProperties" BeforeTargets="GenerateSbomTarget" DependsOnTargets="GetBuildVersion">
    <PropertyGroup>
      <SbomGenerationPackageVersion>$(NuGetPackageVersion)</SbomGenerationPackageVersion>
    </PropertyGroup>
  </Target>

but it would be nice if it worked out of the box.

Originally posted by @KalleOlaviNiemitalo in #693 (comment)

[KalleOlaviNiemitalo]

Based on #693 (comment) and #693 (comment), I think this should be fixed by moving the default values of almost all SBOM-generation properties (but not the GenerateSBOM property) from the top-level PropertyGroup to a new target SetSbomGenerationProperties, on which GenerateSbomTarget would depend; and SetSbomGenerationProperties would depend on GetBuildVersion. That way, if a custom target for non-NuGet packaging uses the GenerateSbom task, it could likewise depend on the SetSbomGenerationProperties target and share the defaulting logic. Other NuGet packages could update the properties in a target that has AfterTargets="SetSbomGenerationProperties", e.g. if they needed to add parameters for some component detectors.