[consutil] Add brief option to show line command

[Blueve]

- What I did

Add --brief and -b option to show line command.
By default, show line command will render a table which includes all console lines in CONSOLE_PORT table and all ttyUSB* devices under \dev. We display ttyUSB* because we want to provide convenience to user when adding console line settings from scratch.
We add this optional option is for reduce noise for some user because the user are not allowed to connect a console line which is not present in CONFIG_DB.

- How I did it

Stop merge console line result into the result table when user specified --brief or -b option.

- How to verify it

Build python-wheel package and tested on physical DUT.

- Previous command output (if the output of a command-line utility has changed)

N/A

- New command output (if the output of a command-line utility has changed)

admin@sonic:~$ sudo show line -b
  Line    Baud    PID    Start Time    Device
------  ------  -----  ------------  --------
     1  115000                        switch1
     2    9600                              -