Existing Embedded Client fails creation of other Embedded Client instances for the same port

[Spikhalskiy]

Current Behavior

Currently, if I attempt to do

    client1 = weaviate.connect_to_embedded()
    client2 = weaviate.connect_to_embedded()

The following error is thrown:

weaviate.exceptions.WeaviateStartUpError: Embedded DB did not start because processes are already listening on ports http:8079 and grpc:50050use weaviate.connect_to_local(port=8079, grpc_port=50050) to connect to the existing instance

This is not just inconvenient and calling for the need for the embedded client to be a singleton, but it's contradicting the method specification, as according to it, the embedded client can be created and used as a context manager:

Alternatively, you can use the client as a context manager
in a `with` statement, which will automatically close the connection when the context is exited.

################## With Context Manager #############################
>>> import weaviate
>>> with weaviate.connect_to_embedded(port=8080, grpc_port=50051) as client:

It will only work if no two threads ever create a context manager for a client on the same port.

Expected behavior

connect_to_embedded and use_async_with_embedded should allow multiple instances to be created with the same ports. This will be a convenient and compliant implementation.