PackageDownload version range implementation

[nkolev92]

There are some considerations here:

• How will the user know that which version got resolved.
• Especially with the potential for duplicate IDs.
• Make sure that the bumped up version warnings are reported.

Note: Search for TODO https://github.com/NuGet/Home/issues/7709 in the code when implementing.

Related to #7339

[nkolev92]

We might need this in 3.1, but there's no exact plans yet.

[scottdallamura]

this would be really nice to have.

scenario:
we are implementing Microsoft.DoNet.ApiCompat checks and to make it super smooth we want to reference the previously-published version of our package. with <PackageDownload> we can do that without any dependency cycles... however since it requires an explicit version, this would require us to manually edit the csproj after each publish with the newly-published version, so it keeps an error-prone human element in the process.

currently we are generating a second "OurLibrary.Baseline" package (to avoid cycles) and using that as the "contract" for ApiCompat

<PackageReference Include="OurLibrary.Baseline" Version="1.*"  GeneratePathProperty="true" />

[ericstj]

The lack of this feature leads to gaps in the package Validation experience see dotnet/sdk#25268. It would be nice to have this as it would help us fill a gap that users are hacking around at the moment.

[Nirmal4G]

It seems to me, people were using PackageDownload items just like PackageReference except the consuming assets part. The team could have just either copy/paste the PackageReference code up until the download part or conditioned the consuming asset's part and be done with it.

This could've been a one-time thing and they could've focused their efforts on other issues that need fresh implementation.

But I did foresee this and I did exactly that, though not perfect it still works. As I said here #11720 (comment) I'll be happy if the team also updates the PackageDownload feature with #8476. Then, I can delete my custom/duplicated code.