Normalize keystore type and its usage across tests (#12553)

* Normalize keystore type and usage across tests

* Extract peer index from array index

substrate/Cargo.lock

@@ -7846,6 +7846,7 @@ dependencies = [
  "sp-core",
  "sp-inherents",
  "sp-io",
+ "sp-keyring",
  "sp-keystore",
  "sp-runtime",
  "sp-timestamp",
@@ -7853,7 +7854,6 @@ dependencies = [
  "sp-version",
  "substrate-prometheus-endpoint",
  "substrate-test-runtime-client",
- "tempfile",
  "thiserror",
 ]
 
@@ -8130,7 +8130,6 @@ dependencies = [
  "sp-tracing",
  "substrate-prometheus-endpoint",
  "substrate-test-runtime-client",
- "tempfile",
  "thiserror",
  "tokio",
 ]