Allow incremental servicing of packages and more packaging infra cleanup

[ViktorHofer]

Requires dotnet/arcade#6728
Based on the discussion in #46180

This PR further cleans up the packaging infra and allows "incremental servicing" at project level instead of traversal level (as it was before for libraries). By default, nuget csprojs or pkgprojs will be built if the <GeneratePackage /> property is set to true.

The GeneratePackage property is currently conditioned as:

    <GeneratePackage Condition="(('$(PreReleaseVersionLabel)' != 'servicing' and
                                  '$(RepositoryName)' != 'runtimelab') or
                                 '$(BuildAllProjects)' != 'true')">true</GeneratePackage>

This means that during servicing or as part of runtimelab, root builds won't generate packages unless a project opts in via <GeneratePackage />. <BuildAllProjects /> identifies a builds as a root build (vs an individual project build: dotnet pack ...).

I wasn't sure how to condition runtimelab so I used the RepositoryName property for now.

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Issue Details

---

Requires dotnet/arcade#6728
Based on the discussion in #46180

This further clean-up allows "incremental servicing" at project level instead of traversal level as it was before for libraries. By default, none nuget csprojs or pkgprojs will be built if the <GeneratePackage /> property isn't set to true.

The GeneratePackage property is currently conditioned as:

    <GeneratePackage Condition="(('$(PreReleaseVersionLabel)' != 'servicing' and
                                  '$(RepositoryName)' != 'runtimelab') or
                                 '$(BuildAllProjects)' != 'true')">true</GeneratePackage>

I wasn't sure how to condition runtimelab so I used the RepositoryName property for now.

Author:	ViktorHofer
Assignees:	ViktorHofer
Labels:	area-Infrastructure
Milestone:	-

[Anipik]

Packing changes for the libraries looks good. I believe there are no functional change in coreclr related changes. its seem like just refactoring ?

[ViktorHofer]

The change applies to all packages in the repo that use the nuget pack task or pkgprojs. It means that no packages will be generated in servicing by default unless we set the to true in their project file. I'm unsure which packages we always want to generate but I assume the sfx ones?

[ViktorHofer]

Timeout is #46484

[jkotas]

How is the RepositoryName meant to be set in runtimelab?