feat: Drop loguru and use builtin logging (#1133)

* Configure simple builtin logging

Changed the 2 existing `print` in the `private_gpt` code base into actual python logging, stop using loguru (dependency will be dropped in a later commit).
Try to use the `key=value` logging convention in logs (to indicate what dynamic values represents, and what is dynamic vs not).
Using `%s` log style, so that the string formatting is pushed inside the logger, giving the ability to the logger to determine if the string need to be formatted or not (i.e. strings from debug logs might not be formatted if the log level is not debug)
The (basic) builtin log configuration have been placed in `private_gpt/__init__.py` in order to initialize the logging system even before we start to launch any python code in `private_gpt` package (ensuring we get any initialization log formatted as we want to)
Disabled `uvicorn` custom logging format, resulting in having uvicorn logs being outputted in our formatted.

Some more concise format could be used if we want to, especially:
```
COMPACT_LOG_FORMAT = '%(asctime)s.%(msecs)03d [%(levelname)s] %(name)s - %(message)s'
```

Python documentation and cookbook on logging for reference:
* https://docs.python.org/3/library/logging.html
* https://docs.python.org/3/howto/logging.html

* Removing loguru from the dependencies

Result of `poetry remove loguru`

* PR feedback: using `logger` variable name instead of `log`

---------

Co-authored-by: Louis Melchior <louis@jaris.io>

private_gpt/settings/settings_loader.py

@@ -1,4 +1,5 @@
 import functools
+import logging
 import os
 import sys
 from pathlib import Path
@@ -9,6 +10,8 @@ from pydantic.v1.utils import deep_update, unique_list
 from private_gpt.constants import PROJECT_ROOT_PATH
 from private_gpt.settings.yaml import load_yaml_with_envvars
 
+logger = logging.getLogger(__name__)
+
 _settings_folder = os.environ.get("PGPT_SETTINGS_FOLDER", PROJECT_ROOT_PATH)
 
 # if running in unittest, use the test profile
@@ -41,7 +44,7 @@ def load_profile(profile: str) -> dict[str, Any]:
 
 def load_active_profiles() -> dict[str, Any]:
     """Load active profiles and merge them."""
-    print(f"Starting application with profiles: {active_profiles}")
+    logger.info("Starting application with profiles=%s", active_profiles)
     loaded_profiles = [load_profile(profile) for profile in active_profiles]
     merged: dict[str, Any] = functools.reduce(deep_update, loaded_profiles, {})
     return merged