[Draft] Add remote compatible show ip bgp and -n all for show ip bgp network

[BYGX-wcr]

What I did

I enable the direct execution of "show ip bgp" on chassis supervisor and "-n all" option for "show ip bgp network" on multi-asic machine

How I did it

1. I modified the show ip bgp command to detect whether the current machine is a supervisor. If so, it will invoke rexec.cli to remotely exec the command on all linecards.
2. I add code in show ip bgp network command to pull the list of namespaces of the current device and run the command for each namespace.

How to verify it

On chassis supervisor, run "show ip bgp ..."
On a multi-asic device, run "show ip bgp network -n all"

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

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

[wenyiz2021]

I know you are just keeping original logic here, that if it is multi-asic, and namespace is not provided, error out.
but I think original logic may not be updated, can you change to: if multi asic, and namespace is not provided, print for all asics?
refer to: #2427
another pros for this is, you are running this cmd on sup, if one chassis has both multi/single-asic LCs, show ip bgp sum will output for all LCs, instead of having multi-asic LC error out, in this case we could have at least cmd working for both multi/single-asic.