Config for web3signer keep-alive (#5007)

* Allow tweaking connection pool settings

* Build docker image

* Fix imports

* Merge tag 'v4.6.0' into web3signer-keep-alive

v4.6.0

* Delete temp docker build stuff

* Fix tests

* Merge remote-tracking branch 'origin/unstable' into web3signer-keep-alive

* Update CLI text

validator_client/src/lib.rs

@@ -192,6 +192,7 @@ impl<T: EthSpec> ProductionValidatorClient<T> {
         let validators = InitializedValidators::from_definitions(
             validator_defs,
             config.validator_dir.clone(),
+            config.clone(),
             log.clone(),
         )
         .await