[tools] support key rotation offer capability in libra-txs

[0xzoz]

Want to allow delegating key rotation to another user, e.g. alice delegates key rotation to bob, such that bob can rotate alice's key

• add test for key rotation cli
• add cli command to offer rotation capability to another user
• add test for offer rotation capability cli
• Add test to validate that bob indeed can rotatte a key for alice
• add cli command to revoke rotation capability
• add test to ensure that bob no longer can rotate alice's key
• enhance key-rotation cli to supply target address to rotate keys for, e.g. bob can specify alice's address to rotate keys on her behalf
  New cli to offer/revoke rotation capability:

libra-txs  user rotation-capability --help
Offer rotation capability to a delegate address. A delegate address now can rotate a key for this account owner

Usage: libra-txs user rotation-capability --action <ACTION> --delegate-address <DELEGATE_ADDRESS>

Options:
  -a, --action <ACTION>                      
  -d, --delegate-address <DELEGATE_ADDRESS>  
  -h, --help

updated rotate-key cli:

libra-txs  user  rotate-key --help
Usage: libra-txs user rotate-key [OPTIONS]

Options:
  -n, --new-private-key <NEW_PRIVATE_KEY>
          The new authkey to be used
  -a, --account-address <ACCOUNT_ADDRESS>
          Account address for which rotation is done. It can be different from caller's address if rotation capability has been granted to the caller. Do not specify this if you want to rotate your own key

Question: I have a few tests failed. Is it expected? It doesn't look like it is related ot my changes by who knows?
failures:
smoke_upgrade_mainnet_compatible_libra
smoke_upgrade_mainnet_compatible_multiple
smoke_upgrade_mainnet_force_libra
smoke_upgrade_mainnet_force_multiple