Partially move document formatting to server side

[kapilmb]

This is one step closer towards moving document formatting completely to server side. The logic could not be moved completely because vscode doesn't appear to send updated values of tabSize and insertSpaces when sending textDocument/formatting or any other formatting related request. Hence, we register the providers on the client side and then manually send the textDocument/rangeFormatting request. The code is designed such that even textDocument/formatting and textDocument/onTypeFormatting requests are handled by textDocument/rangeFormatting. This is done to minimize code duplication.

As and when the tabSize and insertSpaces issues get resolved, we will only need to enable the formatting capabilities on server and add a textDocument/onTypeFormatting handler to completely move formatting to server-side.

Related PRs:

• Add request handlers for document formatting PowerShellEditorServices#516
• Add a Range parameter to Invoke-Formatter cmdlet PSScriptAnalyzer#780

This and the related PRs should also help use resolve the following issues:

• Formatting with formatOnSave causes file to be dirty after save #734
• Never ending "Formatting Powershell document ..." #869

[daviwil]

So happy this is gone now!

[daviwil]

Looks great!