Update to latest PSScriptAnalyzer

[rkeithhill]

We're currently shipping 1.7.0 and should update to 1.8.0 (at least) for the upcoming 0.8.0 release. It has a few goodies we want IMO: https://github.com/PowerShell/PSScriptAnalyzer/blob/development/CHANGELOG.MD

[kapilmb]

We do not ship PSScriptAnalyzer with VSCode anymore. EditorServices depends on an already installed PSScriptAnalyzer module.

[daviwil]

For the moment we do still ship PSSA with the VS Code extension, but I'd like to avoid that in the future. I'll make sure we're tracking that appropriately. For 0.8.0 we'll need to include PSSA until we do the work to make a smooth transition to a non-bundled PSSA.

[daviwil]

Tracking the unbundling of the module here: PowerShell/vscode-powershell#360

[kapilmb]

Got it!

[daviwil]

I'm bundling PSScriptAnalyzer 1.9.0 with the 0.8.0 release of the VS Code extension.