Add metrics inside fork-choice crate (#6205)

* Add metrics inside fork-choice crate

consensus/fork_choice/src/metrics.rs

@@ -0,0 +1,62 @@
+pub use lighthouse_metrics::*;
+use std::sync::LazyLock;
+use types::EthSpec;
+
+use crate::{ForkChoice, ForkChoiceStore};
+
+pub static FORK_CHOICE_QUEUED_ATTESTATIONS: LazyLock<Result<IntGauge>> = LazyLock::new(|| {
+    try_create_int_gauge(
+        "fork_choice_queued_attestations",
+        "Current count of queued attestations",
+    )
+});
+pub static FORK_CHOICE_NODES: LazyLock<Result<IntGauge>> = LazyLock::new(|| {
+    try_create_int_gauge("fork_choice_nodes", "Current count of proto array nodes")
+});
+pub static FORK_CHOICE_INDICES: LazyLock<Result<IntGauge>> = LazyLock::new(|| {
+    try_create_int_gauge(
+        "fork_choice_indices",
+        "Current count of proto array indices",
+    )
+});
+pub static FORK_CHOICE_DEQUEUED_ATTESTATIONS: LazyLock<Result<IntCounter>> = LazyLock::new(|| {
+    try_create_int_counter(
+        "fork_choice_dequeued_attestations_total",
+        "Total count of dequeued attestations",
+    )
+});
+pub static FORK_CHOICE_ON_BLOCK_TIMES: LazyLock<Result<Histogram>> = LazyLock::new(|| {
+    try_create_histogram(
+        "beacon_fork_choice_process_block_seconds",
+        "The duration in seconds of on_block runs",
+    )
+});
+pub static FORK_CHOICE_ON_ATTESTATION_TIMES: LazyLock<Result<Histogram>> = LazyLock::new(|| {
+    try_create_histogram(
+        "beacon_fork_choice_process_attestation_seconds",
+        "The duration in seconds of on_attestation runs",
+    )
+});
+pub static FORK_CHOICE_ON_ATTESTER_SLASHING_TIMES: LazyLock<Result<Histogram>> =
+    LazyLock::new(|| {
+        try_create_histogram(
+            "beacon_fork_choice_on_attester_slashing_seconds",
+            "The duration in seconds on on_attester_slashing runs",
+        )
+    });
+
+/// Update the global metrics `DEFAULT_REGISTRY` with info from the fork choice.
+pub fn scrape_for_metrics<T: ForkChoiceStore<E>, E: EthSpec>(fork_choice: &ForkChoice<T, E>) {
+    set_gauge(
+        &FORK_CHOICE_QUEUED_ATTESTATIONS,
+        fork_choice.queued_attestations().len() as i64,
+    );
+    set_gauge(
+        &FORK_CHOICE_NODES,
+        fork_choice.proto_array().core_proto_array().nodes.len() as i64,
+    );
+    set_gauge(
+        &FORK_CHOICE_INDICES,
+        fork_choice.proto_array().core_proto_array().indices.len() as i64,
+    );
+}