Build installers at the end of the repo build

[ViktorHofer]

Build the Installer projects after everythign else got built by adding a new Traversal project that
builds all P2Ps in it in parallel.

Fixes #58984 Unblocks dotnet/sdk#44828

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Summary of the changes (Less than 80 chars)

Description

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Fixes #{bug number} (in this specific format)

[dotnet-policy-service]

Hey @dotnet/aspnet-build, looks like this PR is something you want to take a look at.

[ViktorHofer]

Adding the NO MERGE label until I fully tested the changes inside the VMR