Unify execution layer endpoints (#3214)

## Issue Addressed

Resolves #3069 

## Proposed Changes

Unify the `eth1-endpoints` and `execution-endpoints` flags in a backwards compatible way as described in https://github.com/sigp/lighthouse/issues/3069#issuecomment-1134219221

Users have 2 options:
1. Use multiple non auth execution endpoints for deposit processing pre-merge
2. Use a single jwt authenticated execution endpoint for both execution layer and deposit processing post merge

Related https://github.com/sigp/lighthouse/issues/3118

To enable jwt authenticated deposit processing, this PR removes the calls to `net_version` as the `net` namespace is not exposed in the auth server in execution clients. 
Moving away from using `networkId` is a good step in my opinion as it doesn't provide us with any added guarantees over `chainId`. See https://github.com/ethereum/consensus-specs/issues/2163 and https://github.com/sigp/lighthouse/issues/2115


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

beacon_node/execution_layer/src/lib.rs

@@ -6,10 +6,10 @@
 
 use crate::engine_api::Builder;
 use crate::engines::Builders;
-use auth::{Auth, JwtKey};
+use auth::{strip_prefix, Auth, JwtKey};
 use engine_api::Error as ApiError;
 pub use engine_api::*;
-pub use engine_api::{http, http::HttpJsonRpc};
+pub use engine_api::{http, http::deposit_methods, http::HttpJsonRpc};
 pub use engines::ForkChoiceState;
 use engines::{Engine, EngineError, Engines, Logging};
 use lru::LruCache;
@@ -42,6 +42,9 @@ mod metrics;
 mod payload_status;
 pub mod test_utils;
 
+/// Indicates the default jwt authenticated execution endpoint.
+pub const DEFAULT_EXECUTION_ENDPOINT: &str = "http://localhost:8551/";
+
 /// Name for the default file used for the jwt secret.
 pub const DEFAULT_JWT_FILE: &str = "jwt.hex";
 
@@ -130,14 +133,6 @@ pub struct Config {
     pub default_datadir: PathBuf,
 }
 
-fn strip_prefix(s: &str) -> &str {
-    if let Some(stripped) = s.strip_prefix("0x") {
-        stripped
-    } else {
-        s
-    }
-}
-
 /// Provides access to one or more execution engines and provides a neat interface for consumption
 /// by the `BeaconChain`.
 ///