[Revamp pipeline thread handling] Restore dialogue about PackageManagement installation

[rjmholt]

From #1459 (comment).

The ExecutePSCommandAsync() API should allow us to both print errors to the console and throw them to the caller so they can take appropriate action.

Then we can use a try/catch at the callsite to handle the behaviour accordingly.

[andyleejordan]

@SydneyhSmith We need to decide if now is the time to remove all our workflows around package management, as it may not be the extension's place to deal with it.

[SydneyhSmith]

@andschwa I cant see anywhere PackageManagement is used by the extension so I am okay with not adding this back, and waiting for customer asks for it (reading back through old issues and PRs I am just seeing issues with it)...that being said I am totally open to the possibility that I am missing an important reason why this exists and would be happy to schedule time to add it back if that reason rises to the surface...

[SeeminglyScience]

Sorry I didn't see this. It's less to do with our workflows and more due to an old version of PackageManagement was causing dead locks due to some of the async stuff they were doing.

See #762

That old version may no longer cause the dead lock though, since we are no longer dependent on PowerShell's event system. Needs testing to be sure though.

[SydneyhSmith]

Thanks @SeeminglyScience that's super helpful

[SeeminglyScience]

Yeah I think we can strip all of this out now. Went into Windows PowerShell, reverted to stock PackageManagement and PowerShellGet, and intellisense no longer dead locks. Then if I go back to stable and I do Find-Package -<tab> it immediately dead locks.

This makes sense since we're no longer using the OnIdle event, so PackageManagement is now able to successfully marshal back to the pipeline thread. Side note, that does also mean PowerShell eventing is working in some respect.

This is also good news because it means anyone who has been ignoring our prompt will now magically get way more stable 🎉