Add functions for complete API parity with legacy history API

[poplexity]

Per https://eosio.github.io/history-tools/wasm-ql.html almost all of the legacy API functions are available via wasm-ql based functions. It looks like only 2 are missing:

get_key_accounts
get_controlled_accounts

The critical one get_key_accounts is used by almost all wallets to discover accounts after a user imports an existing key. Without this node operators will be quite discouraged from cutting over as they likely would need to run an alternative solution just for get_key_accounts calls.