[Feature Request] make validator backend optional for certain use case

Feature Request

Motivation

Is your feature request related to a problem? Please describe.

This is not a problem, but it would make the tool easier to use.

Pitch

Make the validator backend not required for some cases (like get validator-set, validator-config). It would work if I provide a fake vault config. it won’t decrypt validator address, but it’s fine. would be great if we can make the backend optional, so that it’s easier to use

Current:

~/diem/target/debug/diem-operational-tool validator-set --json-server "https://premainnet.libra.org"
error: The following required arguments were not provided:
    --validator-backend <validator-backend>

Suggestion: ~/diem/target/debug/diem-operational-tool validator-set --json-server "https://premainnet.libra.org" This should just print whatever it can print without accessing vault, like account address, node name etc. e.g.

 {
      "name": "figment",
      "account_address": "23116a30dbd95f862c09329acdcecedf",
      "consensus_public_key": "273aeb8282f0d808013837e88caf33586266869fd41a42d5bcc8c91b13ba69c5",
      "fullnode_network_address": "/ip4/35.203.36.131/tcp/6182/ln-noise-ik/466353f41695e99d5007e52fd1ea197d881c079dcc98d86ee1bf7c1b5c03b220/ln-handshake/0",
      "validator_network_address": "/dns4/could-not-decrypt"
    }

Additional context