VSSolutionManager.EnsureInitializeAsync should not subscribe to SolutionEvents multiple times when the project initialization fails #12044

Say you have a large solution with many projects and EnsureInitializeAsync runs.
We get through the InitializeAsync part which adds listeners to the solution events and later we fail by throwing in EnsureNuGetAndVsProjectAdapterCacheAsync.

We can do one of the following:

• We already differentiate between cache initialization and overall initializaiton. It'd be cheap to just set initialize even if the cache initialization fails, but obviously let the cache initialization fail.
• Introduce another init concept, potentially one that unsubscribes when cache initialization fails inside of EnsureInitializeAsync

I am leaning toward the first approach, but this requires more thought.

Related internal issue 1591242