Add support for command [JSON.ARRLEN]

[jujiale]

Implement [JSON.ARRLEN] command
Report the length of the JSON array at path in key
JSON.ARRLEN key [path]

Return
JSON.ARRLEN returns an array of integer replies, an integer for each matching value, each is the array's length, or nil, if the matching value is not an array.

refer to json.arrlen
Add unit and integration tests

[jujiale]

@JyotinderSingh hello, I will add this command for dice. please assign it to me. thanks.

[JyotinderSingh]

@JyotinderSingh hello, I will add this command for dice. please assign it to me. thanks.

Thanks @jujiale! Assigned

[arpitbbhayani]

#488