[show][vrf] Improve the speed of show command for vrf

[MuLinForest]

What I did

Improve the speed of show vrf command

How I did it

It would get interface information from configDB each time for each vrf in vrfs, and if the amount of vrf is large, the command will take much time. Therefore, it will reduce the execution time to let it just get interface information once, and using it with all vrf.

How to verify it

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)

Signed-off-by: MuLin [email protected]

[gord1306]

/azp run

[azure-pipelines[bot]]

Commenter does not have sufficient privileges for PR 2080 in repo Azure/sonic-utilities