Remove snapshot cache related code (#5661)

Squashed commit of the following:

commit 1378a62
Author: Michael Sproul <michael@sigmaprime.io>
Date:   Tue Apr 30 17:02:25 2024 +1000

    Add state cache CLI tests

commit 470134b
Author: Michael Sproul <michael@sigmaprime.io>
Date:   Tue Apr 30 16:43:07 2024 +1000

    Remove cache miss comment entirely

commit 65eee99
Author: Michael Sproul <micsproul@gmail.com>
Date:   Tue Apr 30 16:41:28 2024 +1000

    Fix default state cache size in docs

commit 64db49a
Author: Jimmy Chen <jchen.tc@gmail.com>
Date:   Tue Apr 30 11:51:10 2024 +1000

    Remove snapshot cache and other references.

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -4415,12 +4415,6 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             if cached_head.head_block_root() == parent_block_root {
                 (Cow::Borrowed(head_state), cached_head.head_state_root())
             } else {
-                info!(
-                    self.log,
-                    "Missed snapshot cache during withdrawals calculation";
-                    "slot" => proposal_slot,
-                    "parent_block_root" => ?parent_block_root
-                );
                 let block = self
                     .get_blinded_block(&parent_block_root)?
                     .ok_or(Error::MissingBeaconBlock(parent_block_root))?;

beacon_node/beacon_chain/src/metrics.rs

@@ -32,18 +32,11 @@ lazy_static! {
         "beacon_block_processing_successes_total",
         "Count of blocks processed without error"
     );
+    // Keeping the existing "snapshot_cache" metric name as it would break existing dashboards
     pub static ref BLOCK_PROCESSING_SNAPSHOT_CACHE_SIZE: Result<IntGauge> = try_create_int_gauge(
         "beacon_block_processing_snapshot_cache_size",
         "Count snapshots in the snapshot cache"
     );
-    pub static ref BLOCK_PROCESSING_SNAPSHOT_CACHE_MISSES: Result<IntCounter> = try_create_int_counter(
-        "beacon_block_processing_snapshot_cache_misses",
-        "Count of snapshot cache misses"
-    );
-    pub static ref BLOCK_PROCESSING_SNAPSHOT_CACHE_CLONES: Result<IntCounter> = try_create_int_counter(
-        "beacon_block_processing_snapshot_cache_clones",
-        "Count of snapshot cache clones"
-    );
     pub static ref BLOCK_PROCESSING_TIMES: Result<Histogram> =
         try_create_histogram("beacon_block_processing_seconds", "Full runtime of block processing");
     pub static ref BLOCK_PROCESSING_BLOCK_ROOT: Result<Histogram> = try_create_histogram(