Set epochs-per-blob-prune default to 256 (#7113)

Partially #7100


  Set blob pruning to default to once per day

beacon_node/src/cli.rs

@@ -1009,7 +1009,7 @@ pub fn cli_app() -> Command {
                        database when they are older than the data availability boundary \
                        relative to the current epoch.")
                 .action(ArgAction::Set)
-                .default_value("1")
+                .default_value("256")
                 .display_order(0)
         )
         .arg(

book/src/help_bn.md

@@ -118,7 +118,7 @@ Options:
       --epochs-per-blob-prune <EPOCHS>
           The epoch interval with which to prune blobs from Lighthouse's
           database when they are older than the data availability boundary
-          relative to the current epoch. [default: 1]
+          relative to the current epoch. [default: 256]
       --epochs-per-migration <N>
           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

lighthouse/tests/beacon_node.rs

@@ -1972,7 +1972,7 @@ fn prune_blobs_on_startup_false() {
 fn epochs_per_blob_prune_default() {
     CommandLineTest::new()
         .run_with_zero_port()
-        .with_config(|config| assert!(config.store.epochs_per_blob_prune == 1));
+        .with_config(|config| assert_eq!(config.store.epochs_per_blob_prune, 256));
 }
 #[test]
 fn epochs_per_blob_prune_on_startup_five() {