Remove all prod eth1 related code (#7133)

N/A


  After the electra fork which includes EIP 6110, the beacon node no longer needs the eth1 bridging mechanism to include new deposits as they are provided by the EL as a `deposit_request`. So after electra + a transition period where the finalized bridge deposits pre-fork are included through the old mechanism, we no longer need the elaborate machinery we had to get deposit contract data from the execution layer.

Since holesky has already forked to electra and completed the transition period, this PR basically checks to see if removing all the eth1 related logic leads to any surprises.

book/src/help_bn.md

@@ -122,15 +122,6 @@ Options:
           The number of epochs to wait between running the migration of data
           from the hot DB to the cold DB. Less frequent runs can be useful for
           minimizing disk writes [default: 1]
-      --eth1-blocks-per-log-query <BLOCKS>
-          Specifies the number of blocks that a deposit log query should span.
-          This will reduce the size of responses from the Eth1 endpoint.
-          [default: 1000]
-      --eth1-cache-follow-distance <BLOCKS>
-          Specifies the distance between the Eth1 chain head and the last block
-          which should be imported into the cache. Setting this value lower can
-          help compensate for irregular Proof-of-Work block times, but setting
-          it too low can make the node vulnerable to re-orgs.
       --execution-endpoint <EXECUTION-ENDPOINT>
           Server endpoint for an execution layer JWT-authenticated HTTP JSON-RPC
           connection. Uses the same endpoint to populate the deposit cache.
@@ -454,10 +445,6 @@ Flags:
           resource contention which degrades staking performance. Stakers should
           generally choose to avoid this flag since backfill sync is not
           required for staking.
-      --disable-deposit-contract-sync
-          Explicitly disables syncing of deposit logs from the execution node.
-          This overrides any previous option that depends on it. Useful if you
-          intend to run a non-validating beacon node.
       --disable-enr-auto-update
           Discovery automatically updates the nodes local ENR with an external
           IP address and port as seen by other peers on the network. This
@@ -499,8 +486,6 @@ Flags:
       --enable-private-discovery
           Lighthouse by default does not discover private IP addresses. Set this
           flag to enable connection attempts to local addresses.
-      --eth1-purge-cache
-          Purges the eth1 block and deposit caches
       --genesis-backfill
           Attempts to download blocks all the way back to genesis when
           checkpoint syncing.