Polish Add Python Project flow

[cwebster-99]

When adding a new Python project, using the Add Python Project button on the Python Envs panel doesn't allow users to add a single file although this is supported through the extension. The only way I found to add a single file is by right clicking on the file in the File Explorer and selecting Add Python Project. I would expect these two flows to be unified.

When adding the project via context menu, there is no indicator that anything happened. I would expect a drop down to select the interpreter for the project or some messaging that something happened.

add.project.mp4

[eleanorjboyd]

fixed