Clean up tool execution

[brettcannon]

• Fixes Ensure all promises have exception handlers #327
• Will fix Clean up tool execution in Unit Tests #350
• Will fix Clean up tool execution in Linters #351
• Will fix Clean up tool execution in Formatters #352
• Will fix Clean up tool execution in Refactoring feature of extension #353
• Will fix Clean up tool execution in Language (usage of Jedi) server #354
• Will fix Use new Environment variable parser in Debugger #361
• Will fix Common code to launch python module or python tool #456

Leaving the following open so as to test them separately.

• Will fix Autocomplete fails with paths listed in PYTHONPATH via .env file #316
• Will fix Editing .env file requires restarting of vscode to detect new values #183