[mod] container: replace uWSGI with Granian

The configuration in Granian is handled with ENVs, much more convenient and practical for updating. The settings have been tested for over two months in a production instance, being usable on small to somewhat large instances without having to modify anything.

It also removes the patch functions and ENVs abstraction from the entrypoint, this makes it possible to run the container with immutable configuration.

In some setups, It may be desired to have the volumes/files under a specific uid/gid (other than searxng:searxng), if the entrypoint has root permissions it will chown automatically on every start, which may not be desired. Explicitly setting the new ENV `FORCE_OWNERSHIP=false` will prevent ownership from being modified.

No manual migration is necessary **unless** the user has changed the default uWSGI configuration or has a very specific setup.

Closes https://github.com/searxng/searxng/issues/4894
Closes https://github.com/searxng/searxng/issues/4818
Closes https://github.com/searxng/searxng/issues/4802

Supersedes https://github.com/searxng/searxng/pull/4596

Related https://github.com/searxng/searxng/discussions/4479

docs/admin/installation-docker.rst

@@ -87,14 +87,9 @@ instance using `docker run <https://docs.docker.com/engine/reference/run/>`_:
    $ docker run --rm \
                 -d -p ${PORT}:8080 \
                 -v "${PWD}/searxng:/etc/searxng" \
-                -e "BASE_URL=http://localhost:$PORT/" \
-                -e "INSTANCE_NAME=my-instance" \
                 searxng/searxng
    2f998.... # container's ID
 
-The environment variables UWSGI_WORKERS and UWSGI_THREADS overwrite the default
-number of UWSGI processes and UWSGI threads specified in `/etc/searxng/uwsgi.ini`.
-
 Open your WEB browser and visit the URL:
 
 .. code:: sh