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/validator_store/Cargo.toml

@@ -4,21 +4,6 @@ version = "0.1.0"
 edition = { workspace = true }
 authors = ["Sigma Prime <contact@sigmaprime.io>"]
 
-[lib]
-name = "validator_store"
-path = "src/lib.rs"
-
 [dependencies]
-account_utils = { workspace = true }
-doppelganger_service = { workspace = true }
-initialized_validators = { workspace = true }
-logging = { workspace = true }
-parking_lot = { workspace = true }
-serde = { workspace = true }
-signing_method = { workspace = true }
 slashing_protection = { workspace = true }
-slot_clock = { workspace = true }
-task_executor = { workspace = true }
-tracing = { workspace = true }
 types = { workspace = true }
-validator_metrics = { workspace = true }