Collect assets file change telemetry

[nkolev92]

Bug

Related: NuGet/Home#6987

Description

I have a theory that a very, very large majority of force restore (or effective VS rebuild) events do not change the assets file.
The idea is that we don't need to do force restore during a rebuild, thus saving CPU time.

In this change, I'll add new properties to the restore event, to help me validate that theory.

• ForceRestore (I know the name is opposite from the property, but that ship has sailed, in vs/nuget/restoreinformation we already have this property so this just makes the values consistent).
• UpdatedAssetsFile - indicates whether the assets file needs to be updated as a consequence of this restore
• UpdatedMSBuildFiles - indicates whether the msbuild files need to be updated as a consequence of this restore
• IsPackageInstallationTrigger - tells that a restore was triggered due to a PM UI or PMC package installation. In this case, we should ignore any no-op specifics.

PR Checklist

• Meaningful title, helpful description and a linked NuGet/Home issue
• Added tests
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc.

[jeffkl]

Looks like tests need to be updated as well...

[nkolev92]

Yeah, I returned from vacation awnd just marked it as ready for review, I thought I had done all the changes, but turns out that's not the case. :D

[nkolev92]

@jeffkl ready now, tests should be passing.