Async Support and Much more!

• Converted all priv levels to be kwargs instead of just args for setup -- simple thing but makes it more readable IMO.
• Added to the Juniper prompt pattern to include matching the RE prompt that is on the line "above" the "normal
  " prompt as this was getting included in command output instead of being seen as part of the prompt by scrapli.
• Convert driver privilege escalation prompts to use regex to match upper and lower case "P" in password prompt
• Fix core drivers to actually allow for users to pass failed_when_contains, textfsm_platform, genie_platform, and default_desired_privilege_level
• Add better exception/message for attempting to send command/config to a connection object that has not been opened
• Add testing for on open/close methods of core drivers
• Add send_config method to send a single configuration string -- this will automagically handle sending a full configuration, breaking it into a list of configs, sending that list with send_configs and then joining the responses into a single Response object... or of course you can just send a single config line with it too!
• Add better handling/logging for SystemSSH transport when key exchange cannot be negotiated
• Convert the _failed() method of MultiResponse to be a property so users can check .failed on a MultiResponse object more intuitively/sanely
• ASYNC ALL THE THINGS... basically only an internal change, but hugely modified the guts of scrapli to try to be able to best support asyncio while still having the same api for sync and async. Again, if you dont care about aysncio this probably doesnt matter at all as all the "public" stuff has not changed for sync versions of things.
• Completely overhaul unit tests -- unit tests now spin up an SSH server using asyncssh, this server is a very basic implementation of an IOSXE device. This fake IOSXE device allows for connecting/sending commands/handling log on stuff like disabling paging all in as close to the real thing as possible while being completely self contained and completely in python. Additionally since there was a lot of changes to break things out to be more granular with the async implementation the testing has evolved to support this.
• Increased all hostname patterns to match up to 63 characters -- this is the hostname length limit for Cisco IOSXE at least and should be a reasonable value that hopefully doesnt really ever need to be changed/expanded now
• Changing logging to create a logger associated with each object instance and include the name/ip of the host in the log name -- should make things a lot nicer with threads/asyncio/etc.
• Moved from tox to using nox for handling tests/linting; originally this was because of some of the unit testing failing when ran via tox (now I believe this was because there was no TERM env var set in tox), but at this point nox is quite nice so we'll stick with it!
• Added exception to be raised when users try to use system transport on Windows
• BUGFIX: Added underscores to hostname patterns for IOSXE, IOSXR, NXOS, and Junos (not valid in EOS at least in my testing)
• No more Windows testing, not worth the effort
• BUGFIX: Added functionality to merge less specific (but matching) host entry data for ssh config file hosts -- meaning that we can now merge attributes from a "*" entry into a more specific host entry (see #21)
• Add dependabot to see how we like having that friend around...
• Moved from tox -> nox; long story as to why, but very much like nox!
• fixed some docstrings and re-added darglint into the mix
• Added a "debug" workflow for connecting to runner containers for testing stuff... hopefully wont need to be used often
• Modified workflows a bit to use nox, add darglint back in, and lint more stuff on weekly build (next weekly build may fail if dev doesnt get pulled into master :))
• Updated readme to include async stuff
• Added a basic async example
• Regen docs