Merge the 1.0.0-preview.4 release branch back to main

[daxian-dbw]

PR Summary

Merge the 1.0.0-preview.4 release branch back to main.

• Update version info for the 1.0.0-preview.4 release.
• Use deploy box and GitHubRelease task to create the GitHub draft release.
• Make sure the Runspace is available when importing the AIShell module and throw otherwise.
  • When validating packages, I found there were rare cases where the Runspace instance passed to the constructor of AIShell.Integration.Channel is null. The constructor is used only in the public static method CreateSingleton which is called from AIShell.psm1 to create a singleton of the Channel type upon importing the AIShell module.
  • In AIShell.psm1, we call CreateSingleton with $host.Runspace to pass in the Runspace instance, and the module's manifest defines PowerShellHostName = 'ConsoleHost', so in theory, $host.Runspace should never be null, but that just happened.
  • I'm guessing it could be related to the CompletionPredictor module loaded from my profile, which attempts to sync with the modules loaded in the default session from a separate Runspace -- somehow, the Channel singleton got created from that separate Runspace instead of the default session -- but I cannot prove it.
  • To address this issue, I added restricted checks in both AIShell.psm1 and the constructor of Channel type, to make sure that a Channel singleton can be created only if the Runspace instance is available. Related changes are in this commit: a447dee.