Use latest .NET 6.0 SDK patch version and update devcontainer to use .NET 6 as well

[Christoph Bergmeister (bergmeister)]

PR Summary

Also update devcontainer to move settings to new places as they moved and make PowerShell the default shell and use normal PowerShell extension as the preview is not that far ahead and always gives a popup to use normal extension unless using insiders.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• Make sure all .cs, .ps1 and .psm1 files have the correct copyright header
• Make sure you've added a new test if existing tests do not effectively test the code changed and/or updated documentation
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready.

[James Truher (JamesWTruher)]

looks fine

[Joel Bennett (Jaykul)]

The thing that I don't understand is why we are always using the oldest supported SDK? Every time I touch this project I have to install some ancient SDK ...