Add CLI command for ECMP calculator

[liorghub]

What I did

I have added a new CLI command for calling ECMP calculator.

How I did it

Add new CLI command. Command handler calls script /usr/bin/ecmp_calc.py

How to verify it

Call command and verify its output.

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)

root@sonic:/home/admin# show ip ecmp-egress-port --ingress-port Ethernet64 --packet /tmp/packet.json
Egress port: Ethernet0
root@sonic:/home/admin# 

[liat-grozovik]

@prsunny could you please review or suggest someone who can?

[liat-grozovik]

missing tests for new code. please add
missing changes in command reference guide. please add

I dont think we should have -i before the interface name. just use the interface name
check for reference 'show interfaces transceiver presence Ethernet0'
same for the -p.

[prsunny]

This is a vendor specific utility. I thought we can directly use the utility to get the hash result. I don't think we need to expose it via a generic CLI command.

[liat-grozovik]

In this case, the utility is already available and readme file explain directly how it can be used.
I was under the impression you would like to have the CLI and if the utility available it will be running.
But if this is not required, we can close this PR and leave with the utility itself.