documentation for searchPaths

[eleanorjboyd]

Given the new settings python-env.workspaceSearchPaths and python-env.globalSearchPaths we should create a doc that explains how they work and how they are transitioning over from the old settings. Also could add in the environment manager specific search paths to explain how those are used too

[eleanorjboyd]

this is now included in our docs! https://code.visualstudio.com/docs/python/environments