Modularize validator store (#6705)

- Create trait `ValidatorStore` with all functions used by the `validator_services`
- Make `validator_services` generic on `S: ValidatorStore`
- Introduce `LighthouseValidatorStore`, which has identical functionality to the old `ValidatorStore`
- Remove dependencies (especially `environment`) from `validator_services` and `beacon_node_fallback` in order to be able to cleanly use them in Anchor

validator_client/http_metrics/src/lib.rs

@@ -2,6 +2,7 @@
 //!
 //! For other endpoints, see the `http_api` crate.
 
+use lighthouse_validator_store::LighthouseValidatorStore;
 use lighthouse_version::version_with_platform;
 use logging::crit;
 use malloc_utils::scrape_allocator_metrics;
@@ -15,7 +16,6 @@ use std::time::{SystemTime, UNIX_EPOCH};
 use tracing::info;
 use types::EthSpec;
 use validator_services::duties_service::DutiesService;
-use validator_store::ValidatorStore;
 use warp::{http::Response, Filter};
 
 #[derive(Debug)]
@@ -36,17 +36,19 @@ impl From<String> for Error {
     }
 }
 
+type ValidatorStore<E> = LighthouseValidatorStore<SystemTimeSlotClock, E>;
+
 /// Contains objects which have shared access from inside/outside of the metrics server.
-pub struct Shared<E: EthSpec> {
-    pub validator_store: Option<Arc<ValidatorStore<SystemTimeSlotClock, E>>>,
-    pub duties_service: Option<Arc<DutiesService<SystemTimeSlotClock, E>>>,
+pub struct Shared<E> {
+    pub validator_store: Option<Arc<ValidatorStore<E>>>,
+    pub duties_service: Option<Arc<DutiesService<ValidatorStore<E>, SystemTimeSlotClock>>>,
     pub genesis_time: Option<u64>,
 }
 
 /// A wrapper around all the items required to spawn the HTTP server.
 ///
 /// The server will gracefully handle the case where any fields are `None`.
-pub struct Context<E: EthSpec> {
+pub struct Context<E> {
     pub config: Config,
     pub shared: RwLock<Shared<E>>,
 }