Implement feerecipient API for keymanager (#3213)

## Issue Addressed

* #3173 

## Proposed Changes

Moved all `fee_recipient_file` related logic inside the `ValidatorStore` as it makes more sense to have this all together there. I tested this with the validators I have on `mainnet-shadow-fork-5` and everything appeared to work well. Only technicality is that I can't get the method to return `401` when the authorization header is not specified (it returns `400` instead). Fixing this is probably quite difficult given that none of `warp`'s rejections have code `401`.. I don't really think this matters too much though as long as it fails.

validator_client/src/lib.rs

@@ -5,7 +5,6 @@ mod check_synced;
 mod cli;
 mod config;
 mod duties_service;
-mod fee_recipient_file;
 mod graffiti_file;
 mod http_metrics;
 mod key_cache;
@@ -360,6 +359,7 @@ impl<T: EthSpec> ProductionValidatorClient<T> {
             context.eth2_config.spec.clone(),
             doppelganger_service.clone(),
             slot_clock.clone(),
+            config.fee_recipient,
             context.executor.clone(),
             log.clone(),
         ));
@@ -426,8 +426,6 @@ impl<T: EthSpec> ProductionValidatorClient<T> {
             .validator_store(validator_store.clone())
             .beacon_nodes(beacon_nodes.clone())
             .runtime_context(context.service_context("preparation".into()))
-            .fee_recipient(config.fee_recipient)
-            .fee_recipient_file(config.fee_recipient_file.clone())
             .build()?;
 
         let sync_committee_service = SyncCommitteeService::new(