Broadcast address changes at Capella (#3919)

* Add first efforts at broadcast

* Tidy

* Move broadcast code to client

* Progress with broadcast impl

* Rename to address change

* Fix compile errors

* Use `while` loop

* Tidy

* Flip broadcast condition

* Switch to forgetting individual indices

* Always broadcast when the node starts

* Refactor into two functions

* Add testing

* Add another test

* Tidy, add more testing

* Tidy

* Add test, rename enum

* Rename enum again

* Tidy

* Break loop early

* Add V15 schema migration

* Bump schema version

* Progress with migration

* Update beacon_node/client/src/address_change_broadcast.rs

Co-authored-by: Michael Sproul <micsproul@gmail.com>

* Fix typo in function name

---------

Co-authored-by: Michael Sproul <micsproul@gmail.com>

Cargo.lock

@@ -1062,8 +1062,10 @@ dependencies = [
  "lazy_static",
  "lighthouse_metrics",
  "lighthouse_network",
+ "logging",
  "monitoring_api",
  "network",
+ "operation_pool",
  "parking_lot 0.12.1",
  "sensitive_url",
  "serde",
@@ -1073,6 +1075,7 @@ dependencies = [
  "slasher_service",
  "slog",
  "slot_clock",
+ "state_processing",
  "store",
  "task_executor",
  "time 0.3.17",
@@ -3224,6 +3227,7 @@ dependencies = [
  "logging",
  "lru 0.7.8",
  "network",
+ "operation_pool",
  "parking_lot 0.12.1",
  "proto_array",
  "safe_arith",
@@ -5007,6 +5011,7 @@ dependencies = [
  "lru_cache",
  "matches",
  "num_cpus",
+ "operation_pool",
  "rand 0.8.5",
  "rlp",
  "slog",
@@ -5342,6 +5347,7 @@ dependencies = [
  "lighthouse_metrics",
  "maplit",
  "parking_lot 0.12.1",
+ "rand 0.8.5",
  "rayon",
  "serde",
  "serde_derive",