Generate SBOM for nuget packages

[Bertk]

Add SBOM files for coverlet nuget packages e.g.

[SimonCropp]

i prefer the more compact version of this. 1 line compared to 4

<PackageReference Include="Microsoft.Sbom.Targets" PrivateAssets="all" />

[Copilot]

Pull Request Overview

This PR adds support for generating SBOM files for NuGet packages across multiple projects by enabling SBOM generation during CI builds and adding the required package references.

• Added the property driven by the TF_BUILD environment variable in three csproj files.
• Included a PackageReference to Microsoft.Sbom.Targets with appropriate PrivateAssets and IncludeAssets settings in the csproj files.
• Updated Directory.Packages.props to pin the Microsoft.Sbom.Targets package version.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/coverlet.msbuild.tasks/coverlet.msbuild.tasks.csproj	Added GenerateSBOM property and Microsoft.Sbom.Targets package reference for SBOM generation.
src/coverlet.console/coverlet.console.csproj	Enabled SBOM generation and added Microsoft.Sbom.Targets package reference.
src/coverlet.collector/coverlet.collector.csproj	Introduced the GenerateSBOM flag and added Microsoft.Sbom.Targets package reference.
Directory.Packages.props	Added package version for Microsoft.Sbom.Targets.

Comments suppressed due to low confidence (7)

src/coverlet.msbuild.tasks/coverlet.msbuild.tasks.csproj:22

• [nitpick] Consider enhancing this comment with details on the expected value of TF_BUILD and the conditions under which SBOM generation occurs to support future maintainability.

<!-- create SBOM for CI build-->

src/coverlet.msbuild.tasks/coverlet.msbuild.tasks.csproj:46

• Verify that the configured PrivateAssets and IncludeAssets for Microsoft.Sbom.Targets conform with the project’s dependency management policies.

<PackageReference Include="Microsoft.Sbom.Targets">

src/coverlet.console/coverlet.console.csproj:9

• [nitpick] Consider adding a brief note about TF_BUILD in this comment to clarify when SBOM generation is enabled during CI builds.

<!-- create SBOM for CI build-->

src/coverlet.console/coverlet.console.csproj:30

• Ensure that the dependency settings (PrivateAssets and IncludeAssets) for Microsoft.Sbom.Targets are consistent with other projects and meet the overall design requirements.

<PackageReference Include="Microsoft.Sbom.Targets">

src/coverlet.collector/coverlet.collector.csproj:21

• [nitpick] Expand this comment to specify what TF_BUILD represents and the scenario under which SBOM generation will be triggered.

<!-- create SBOM for CI build-->

src/coverlet.collector/coverlet.collector.csproj:45

• Review the asset inclusion/exclusion settings for Microsoft.Sbom.Targets to ensure they are optimal and consistent with related projects.

<PackageReference Include="Microsoft.Sbom.Targets">

Directory.Packages.props:32

• Consider using a centralized version variable for Microsoft.Sbom.Targets to maintain consistency across projects, if applicable.

<PackageVersion Include="Microsoft.Sbom.Targets" Version="3.1.0" />