Project wide evaluation in this extension

This request is a transferred from vscode-python on issue https://github.com/microsoft/vscode-python/issues/3836. This issue will be maintained as tracking this feature request for flake8. Please upvote if you would like to demonstrate support/need for this feature, thanks!

Start by reading the transferred vscode-python issue #3836 and the current vscode-flake8 issue context. The payload does not identify files, tests, or an entry point, and it does not define the expected project-wide evaluation behavior, so completion criteria need to be established before implementation.

Written by the indexing model from the issue text.