Exception handling, explicit ssh config, increase default timeouts

• Catch ConnectionLost exception during read operations so we can raise a scrapli exception instead of the asyncssh exception
• Explicitly pass ssh config file to asyncssh -- in this way if the user sets ssh_config_file=False we will make sure that asyncssh ignores the config file
• Bumped up the default timeout values as they were probably a little on the aggressive side -- its user configurable anyway so folks can set this to whatever they feel like!