Rewrite UpdatePowerShell feature

[andyleejordan]

It's way better now, relying on GitHub less and instead mimicking what PowerShell itself does, and resolves #3226.

Requires PowerShell/PowerShellEditorServices#1965.

[andyleejordan]

@SeeminglyScience you can pretty much ignore the change from Logger to ILogger, that was so I could instantiate a TestLogger class that doesn't do anything and pass it along to the constructor of UpdatePowerShell (and probably other things when we get more robust client unit tests).

For Linux, macOS, and unsupported (mostly Arm64) architectures on Windows, the update prompt now opens the user's configured URL handler to the GitHub release for the new release. 🥳 While we never supported auto-updating on Linux, this does mean I took out the brew cask update script for macOS. It can work, but it should only be run if we can assert first that the pwsh we're updating was installed by brew, which we weren't doing and isn't always the case. For instance, I install straight from the .pkg installer and so had turned off the update prompt. Also, we should do it using vscode.env.ShellExecution instead of relying on the language server to run a script (to update its own executable). So I've punted that work because it's complicated and requires an update to do right.

[SeeminglyScience]

LGTM!