Create the first PowerShellManager instance when processing the first FunctionLoad request

[daxian-dbw]

This is to fix the regression in local debugging.
We create the first PowerShellManager instance when processing the first FunctionLoad request, so the debugger has the target Runspace to attach to.
However, we delay the initialization of the first PowerShellManager instance until the first invocation (when checking out the instance from pool).

It turns out we cannot have the dependency manager to create a separate Runspace for downloading.
The VS Code local debugging assumes the target Runspace has Id = 1, which was true before as only one Runspace will be created initially.
Now, the dependency manager creates a separate Runspace for downloading, and there will be a race condition -- sometimes the Runspace created for the downloading has Id = 1, and thus the debugger will attach to that Runspace, which will be reclaimed after the download and causing the Wait-Debugger in the user's function script to not be hit.

This refactoring make sure only one Runspace is created initially -- the PowerShell instance used for the downloading is also used to serve the first invocation request.
So there is no race condition and local debugging can work reliably.

Fix #196.

[daxian-dbw]

@TylerLeonhardt, I made more changes on top of #200 than I thought, so I just pushed a separate PR.

[TylerLeonhardt]

LGTM

[daxian-dbw]

It turns out we cannot have the dependency manager to create a separate Runspace for downloading.
The VS Code local debugging assumes the target Runspace has Id = 1, which was true before as only one Runspace will be created initially.
Now, the dependency manager creates a separate Runspace for downloading, and there will be a race condition -- sometimes the Runspace created for the downloading has Id = 1, and thus the debugger will attach to that Runspace, which will be reclaimed after the download and causing the Wait-Debugger in the user's function script to not be hit.

This refactoring make sure only one Runspace is created initially -- the PowerShell instance used for the downloading is also used to serve the first invocation request.
So there is no race condition and local debugging can work reliably.

[daxian-dbw]

@TylerLeonhardt and @SatishRanjan Can you both please review this PR again? Thanks

Design changed, need to be reviewed again.

[TylerLeonhardt]

LGTM!

[Francisco-Gamino]

LGTM. Thank you @daxian-dbw for fixing the local debugging issue!