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'

.github/workflows/build_khoj_el.yml

@@ -7,13 +7,13 @@ on:
     branches:
       - 'master'
     paths:
-      - src/interface/emacs/*.el
+      - src/khoj/interface/emacs/*.el
       - .github/workflows/build_khoj_el.yml
   pull_request:
     branches:
       - 'master'
     paths:
-      - src/interface/emacs/*.el
+      - src/khoj/interface/emacs/*.el
       - .github/workflows/build_khoj_el.yml
 
 jobs:
@@ -33,7 +33,7 @@ jobs:
     - name: Run
       env:
         # Khoj recipe from https://github.com/melpa/melpa/pull/8321/files
-        RECIPE: (khoj :fetcher github :repo "debanjum/khoj" :files ("src/interface/emacs/*.el"))
+        RECIPE: (khoj :fetcher github :repo "debanjum/khoj" :files ("src/khoj/interface/emacs/*.el"))
         EXIST_OK: true
         LOCAL_REPO: ${{ github.workspace }}
       run: echo $GITHUB_REF && make -C ~/melpazoid