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'

.gitignore

@@ -1,7 +1,6 @@
 # Khoj artifacts
 *.gz
 *.pt
-src/.data
 tests/data/models
 tests/data/embeddings
 
@@ -13,10 +12,10 @@ __pycache__
 .vscode
 
 # Build artifacts
-/src/interface/web/images
+/src/khoj/interface/web/images
 /build/
 /dist/
-/khoj_assistant.egg-info/
+khoj_assistant.egg-info
 /config/khoj*.yml
 .pytest_cache
 khoj.log