Use the src/ layout to fix packaging Khoj for PyPi

- Why
  The khoj pypi packages should be installed in `khoj' directory.
  Previously it was being installed into `src' directory, which is a
  generic top level directory name that is discouraged from being used

- Changes
 - move src/* to src/khoj/*
 - update `setup.py' to `find_packages' in `src' instead of project root
 - rename imports to form `from khoj.*' in complete project
 - update `constants.web_directory' path to use `khoj' directory
 - rename root logger to `khoj' in `main.py'
 - fix image_search tests to use the newly rename `khoj' logger
 - update config, docs, workflows to reference new path `src/khoj'

MANIFEST.in

@@ -1,5 +1,7 @@
 include README.md
-graft src/interface/*
-prune src/interface/web/images*
+graft src/khoj/interface/*
+prune src/khoj/interface/web/images*
 prune docs*
+prune src/khoj/interface/obsidian*
+prune src/khoj/interface/emacs*
 global-exclude .DS_Store *.py[cod]