Fix installation for library and template packs

[joeloff]

Ensure that library and template packs install directly under the root folder, e.g. dotnet\library-packs (no versioned sub-folders)

[pjcollins]

The only other thing I can think of here is related to dotnet/sdk#17438. The template packs we produce and publish are camel-cased, however dotnet workload install foo does install fully lower-cased template packs into the template-packs folder. This may not matter for the Windows only .msi scenario but it may by worth considering doing the same thing with .msi based installs.

[joeloff]

camel casing won't impact the MSIs, but we do use the package IDs when creating folders. More importantly, the IDs participate in generating some of the GUIDs. For the most part its fine, except in the case of manifests where the MSIs have to be upgradable, so any change in casing could break that.