This PR removes the usage of the custom `mongodb_proxy` package from
edx-platform, replacing it with MongoDB's built-in retry functionality via
`retryReads=True`.
Changes:
* Removed all references to `mongodb_proxy.MongoProxy` from connection logic.
* Updated `connect_to_mongodb()` to always use `retryReads=True`.
* Uninstalled `openedx-mongodbproxy` from edx-platform requirements.
Fixes: https://github.com/openedx/edx-platform/issues/35210
- Moving xmodule folder to root as we're dissolving sub-projects of common folder in edx-platform
- More info: https://openedx.atlassian.net/browse/BOM-2579
- -e common/lib/xmodule has been removed from the requirements as xmodule has itself become the part of edx-platform and not being installed through requirements
- The test files common/lib/xmodule/test_files/ have been removed as they are not being used anymore
