Standard beacon api updates (#1831)

## Issue Addressed

Resolves #1809 
Resolves #1824
Resolves #1818
Resolves #1828 (hopefully)

## Proposed Changes

- add `validator_index` to the proposer duties endpoint
- add the ability to query for historical proposer duties
- `StateId` deserialization now fails with a 400 warp rejection
- add the `validator_balances` endpoint
- update the `aggregate_and_proofs` endpoint to accept an array
- updates the attester duties endpoint from a `GET` to a `POST`
- reduces the number of times we query for proposer duties from once per slot per validator to only once per slot 


Co-authored-by: realbigsean <seananderson33@gmail.com>
Co-authored-by: Paul Hauner <paul@paulhauner.com>

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -984,9 +984,9 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
     ///
     /// - `VerifiedUnaggregatedAttestation`
     /// - `VerifiedAggregatedAttestation`
-    pub fn apply_attestation_to_fork_choice<'a>(
+    pub fn apply_attestation_to_fork_choice(
         &self,
-        verified: &'a impl SignatureVerifiedAttestation<T>,
+        verified: &impl SignatureVerifiedAttestation<T>,
     ) -> Result<(), Error> {
         let _timer = metrics::start_timer(&metrics::FORK_CHOICE_PROCESS_ATTESTATION_TIMES);