Dependencies: Stop bundling client libraries

When installing some of our community modules through extras, we usually bundle a client library for interacting with the service provided from the container. In some cases this is nice, as there is only a single, official client library available for that service (E.g. qdrant-client).

However, in many cases there is no single client library that makes for the best choice. Some examples are sqlalchemy in combination with other drivers for connecting to databses, where you have the choice between multiple drivers (such as pyodbc and pymssql for SQL Server, pg8000 and psycopg for Postgres and so on). Many use cases don't even use sqlalchemy for their database connection, and we are thus forcing an install of one or more useless packages in their builds.

Therefore I suggest that we remove all dependencies for client libraries in our extras and put the responsibility for connecting to the containers with their chosen framework on the users of tc-python. We will still keep client libraries as part of our dev dependencies, so that we can provide usage examples in our doctests and other documentation, but simply installing testcontainers-python with some extras will no longer give you a large bundle of dependencies you might not need.

Where possible, we will still include and maintain methods such as get_connection_string (and variants, where we should probably standardize on a naming convention for consistency) for easy usage with client libraries. Example usage with client libraries also become more important, but in those examples we always show imports of the client library used, so it should be quite self-explanatory that you need a client to connect to a service.

This work has already been partly started, and contain useful discussion around the issue. See here for the work done on removing sqlalchemy from Postgres.