Additional 2.0 INX endpoints

[DaughterOfMars]

Description

Some additional endpoints are needed to support IOTA 2.0:

• read_committee
  Accepts an epochs index and returns the validator committee at that epoch.
  Usage expectation: Tracking committee per epoch for analytics.
• read_output_mana_rewards
  Accepts an output ID and slot index and returns the mana rewards.
  Usage expectation:
  1. Analytics tracking per epoch
  2. Determining burned mana in transactions (something like burned_mana = output_mana - (input_mana + rewards)
     Questions: Is this calculation even possible? Can rewards be partially claimed, or not claimed?
• read_account_ledger
  Not sure about this one, but we need a way to track, at minimum, the size of the account ledger.
  Usage expectation: UTXO ledger size vs Account ledger size analytics