cli: better formatting of lists

[kradalby]

This commit changes lists in cli to be new line instead of commas, making them easier to read when they are large.

Also adds a separator between items in tables with multi lines list.

Fixes #2612

[nblock]

I'm unsure about this specific implementation. It improves readability for headscale nodes list-routes with many routes but headscale nodes list, headscale preauthkeys list -u 1 are just one line per record and are now cluttered with ---…. which makes them hard to read:

headscale preauthkeys list -u 1
ID | Key/Prefix                                       | Reusable | Ephemeral | Used  | Expiration          | Created             | Tags
1  | a23XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX | false    | true      | false | 2022-02-26 17:11:15 | 2022-02-26 17:02:32 |
---------------------------------------------------------------------------------------------------------------------------------------
2  | 9d8XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX | false    | true      | true  | 2022-02-26 17:11:18 | 2022-02-26 17:08:07 |
---------------------------------------------------------------------------------------------------------------------------------------
3  | ef0XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX | false    | false     | true  | 2022-02-26 17:16:54 | 2022-02-26 17:11:54 |
---------------------------------------------------------------------------------------------------------------------------------------
[snipped]

Can we remove the horizontal line for all tables? I think the formatting with be good enough, Would look something like this:

headscale nodes list-routes
ID | Hostname | Approved              | Available             | Serving (Primary)
14 | node1    | 0.0.0.0/0             | 0.0.0.0/0             | 0.0.0.0/0
   |          | ::/0                  | ::/0                  | ::/0
31 | node2    | 10.1.0.0/16           | 10.1.0.0/16           |
   |          | 10.5.0.0/16           | 10.5.0.0/16           |
   |          | 10.26.0.0/16          | 10.26.0.0/16          |
   |          | 10.48.0.0/16          | 10.48.0.0/16          |
   |          | 10.49.0.0/16          | 10.49.0.0/16          |
   |          | 10.101.0.0/16         | 10.101.0.0/16         |
   |          | 10.102.0.0/16         | 10.102.0.0/16         |
   |          | 10.149.0.0/16         | 10.149.0.0/16         |
   |          | 10.200.0.0/16         | 10.200.0.0/16         |
   |          | 10.236.0.0/16         | 10.236.0.0/16         |
   |          | 10.237.0.0/16         | 10.237.0.0/16         |
   |          | 10.238.0.0/16         | 10.238.0.0/16         |
   |          | 172.23.1.9/32         | 172.23.1.9/32         |
   |          | 172.23.1.13/32        | 172.23.1.13/32        |
33 | node3    | 192.168.81.0/24       | 192.168.81.0/24       |
   |          | 192.168.82.0/24       | 192.168.82.0/24       |
   |          | 192.168.83.0/24       | 192.168.83.0/24       |

Or keep the horizontal lines just for headscale nodes list-routes and remove it for all others where output is just one line per record?

headscale nodes list-routes
ID | Hostname | Approved              | Available             | Serving (Primary)
14 | node1    | 0.0.0.0/0             | 0.0.0.0/0             | 0.0.0.0/0
   |          | ::/0                  | ::/0                  | ::/0
---------------------------------------------------------------------------------
31 | node2    | 10.1.0.0/16           | 10.1.0.0/16           |
   |          | 10.5.0.0/16           | 10.5.0.0/16           |
   |          | 10.26.0.0/16          | 10.26.0.0/16          |
   |          | 10.48.0.0/16          | 10.48.0.0/16          |
   |          | 10.49.0.0/16          | 10.49.0.0/16          |
   |          | 10.101.0.0/16         | 10.101.0.0/16         |
   |          | 10.102.0.0/16         | 10.102.0.0/16         |
   |          | 10.149.0.0/16         | 10.149.0.0/16         |
   |          | 10.200.0.0/16         | 10.200.0.0/16         |
   |          | 10.236.0.0/16         | 10.236.0.0/16         |
   |          | 10.237.0.0/16         | 10.237.0.0/16         |
   |          | 10.238.0.0/16         | 10.238.0.0/16         |
   |          | 172.23.1.9/32         | 172.23.1.9/32         |
   |          | 172.23.1.13/32        | 172.23.1.13/32        |
---------------------------------------------------------------------------------
33 | node3    | 192.168.81.0/24       | 192.168.81.0/24       |
   |          | 192.168.82.0/24       | 192.168.82.0/24       |
   |          | 192.168.83.0/24       | 192.168.83.0/24       |