Add support for new get_accounts_by_authorizers API endpoint

[aaroncox]

2.0.6 brings a new API endpoint capable of returning data for key lookups.

# query by key auth
curl -d '{"keys": ["EOS8SZ6u1GyezXy5NWZPU2yoqjXsmx63ZFYDTesXLAHNSQjvw2ses"]}' http://jungle3.greymass.com/v1/chain/get_accounts_by_authorizers

# query by account auth
curl -d '{"accounts": ["eosio"]}' http://jungle3.greymass.com/v1/chain/get_accounts_by_authorizers

These APIs also accept an array of values to query as opposed to just a single query.

Lighthouse should be modified to:

• Use this new API endpoint (when available? get_supported_apis could be used to detect).
• Allow multiple key/account inputs in /lookup

To complete this, we'll need to start upgrading our APIs to 2.0.6

[jnordberg]

Allow multiple key/account inputs in /lookup

I'm hesitant on this, the endpoint is already a potential DDoS amplifier against our entire infra and is designed to cache really well. Adding multi key lookups would require us to switch to a less cache friendly api as well as making it even more of an amplifier