Multi-project restore should be resiliant to one project throwing an unhandled exception

[zivkan]

See also #13085 (comment) and NuGet/NuGet.Client#5608 (review)

If a solution has multiple projects, and RestoreCommand throws an unhandled exception while restoring one project, there should be some kind of graceful error handling, and allow all other projects to restore.

In VS, since restore is triggered every build, this means a restore error could occur very frequently as customers try different things to fix their build. The VS activity log only retains a fixed number of errors, so we should not spam the activity log with the same error over and over. This might mean not reporting these unhandled restore exceptions in the activity log, and recording them another way for us to investigate.

[nkolev92]

You bring up great points, maybe we need to do multiple things:

• Failures within RestoreCommand(NuGet.Commands) should be handle by the restore command itself, and logged through an assets file and all the good stuff.
• Higher lever failures: An idea could be:
  • Try/catch - show an error in the error list.
  • Ensure the error information that's capture within our telemetry.
    • Maybe this is a special type of failure, cause often this means potential bugs in our code. (not always though).