RPC RequestId Cleanup (#7238)

I've been working at updating another library to latest Lighthouse and got very confused with RPC request Ids.

There were types that had fields called `request_id` and `id`. And interchangeably could have types `PeerRequestId`, `rpc::RequestId`, `AppRequestId`, `api_types::RequestId` or even `Request.id`.

I couldn't keep track of which Id was linked to what and what each type meant.

So this PR mainly does a few things:
- Changes the field naming to match the actual type. So any field that has an  `AppRequestId` will be named `app_request_id` rather than `id` or `request_id` for example.
- I simplified the types. I removed the two different `RequestId` types (one in Lighthouse_network the other in the rpc) and grouped them into one. It has one downside tho. I had to add a few unreachable lines of code in the beacon processor, which the extra type would prevent, but I feel like it might be worth it. Happy to add an extra type to avoid those few lines.
- I also removed the concept of `PeerRequestId` which sometimes went alongside a `request_id`. There were times were had a `PeerRequest` and a `Request` being returned, both of which contain a `RequestId` so we had redundant information. I've simplified the logic by removing `PeerRequestId` and made a `ResponseId`. I think if you look at the code changes, it simplifies things a bit and removes the redundant extra info.

I think with this PR things are a little bit easier to reasonable about what is going on with all these RPC Ids.

NOTE: I did this with the help of AI, so probably should be checked

beacon_node/lighthouse_network/src/rpc/self_limiter.rs

@@ -207,7 +207,7 @@ mod tests {
     use crate::rpc::rate_limiter::Quota;
     use crate::rpc::self_limiter::SelfRateLimiter;
     use crate::rpc::{Ping, Protocol, RequestType};
-    use crate::service::api_types::{AppRequestId, RequestId, SingleLookupReqId, SyncRequestId};
+    use crate::service::api_types::{AppRequestId, SingleLookupReqId, SyncRequestId};
     use libp2p::PeerId;
     use logging::create_test_tracing_subscriber;
     use std::time::Duration;
@@ -226,7 +226,7 @@ mod tests {
             Hash256::ZERO,
             &MainnetEthSpec::default_spec(),
         ));
-        let mut limiter: SelfRateLimiter<RequestId, MainnetEthSpec> =
+        let mut limiter: SelfRateLimiter<AppRequestId, MainnetEthSpec> =
             SelfRateLimiter::new(config, fork_context).unwrap();
         let peer_id = PeerId::random();
         let lookup_id = 0;
@@ -234,12 +234,12 @@ mod tests {
         for i in 1..=5u32 {
             let _ = limiter.allows(
                 peer_id,
-                RequestId::Application(AppRequestId::Sync(SyncRequestId::SingleBlock {
+                AppRequestId::Sync(SyncRequestId::SingleBlock {
                     id: SingleLookupReqId {
                         lookup_id,
                         req_id: i,
                     },
-                })),
+                }),
                 RequestType::Ping(Ping { data: i as u64 }),
             );
         }
@@ -256,9 +256,9 @@ mod tests {
             for i in 2..=5u32 {
                 assert!(matches!(
                     iter.next().unwrap().request_id,
-                    RequestId::Application(AppRequestId::Sync(SyncRequestId::SingleBlock {
+                    AppRequestId::Sync(SyncRequestId::SingleBlock {
                         id: SingleLookupReqId { req_id, .. },
-                    })) if req_id == i,
+                    }) if req_id == i,
                 ));
             }
 
@@ -281,9 +281,9 @@ mod tests {
             for i in 3..=5 {
                 assert!(matches!(
                     iter.next().unwrap().request_id,
-                    RequestId::Application(AppRequestId::Sync(SyncRequestId::SingleBlock {
+                    AppRequestId::Sync(SyncRequestId::SingleBlock {
                         id: SingleLookupReqId { req_id, .. },
-                    })) if req_id == i,
+                    }) if req_id == i,
                 ));
             }