Redesigning and renaming abstraction, making it more focused on just the
transport layer communication handling, rather than general service
client behavior; also extending new type with a subtype that adds SSL
context security.

Making RequestClient concrete but generic.

Add ConnectionContextClient as an abstract transport client than
maintains a connection via an async managed context, and
(re)implementing WebSocketClient using the new (secure) transport
client with a context managed connection.

Update specialized clients to extend RequestClient

Fix ExternalClient with changes.

Deprecating to help move away from service-specific types in a general
library.

Updating handlers to account for changes to communication package.

Making this a static method rather than a class method, as it doesn't
need any class details.

Moving to top-level interface rather than having subtype for this.

Removing redundant SSLSecuredTransportLayerClient subtype.

Removing redundant SSLSecuredTransportLayerClient from communication
package __init__.py.

Modifying TransportLayerClient to expect init params for (most of) the
components of a URI, rather than the endpoint URI directly, and adding
abstract property so that concrete types can implement this themselves
(e.g., to control the specific protocol component used in the URI).

Cleaning up TransportLayerClient __init__ to not pass var/keyword args
to super (ABC), and removing abstract annotation from implemented
method in WebSocketClient.

Fixing setup of scheduler client unit tests by adding implementation of
this classmethod, declared as abstract in upstream superclass.

Removing public property in TransportLayerClient and replacing with use
of private attribute.

Clarify that endpoint_host does not include protocol in docstring.

Co-authored-by: Austin Raney <[email protected]>