Removed pub from some functions which are actually private to improve encapsulation (#18030)

Remove the pub marker to improve encapsulation. Readability improvement only, no functional impact.

core/src/banking_stage.rs

@@ -628,7 +628,7 @@ impl BankingStage {
     }
 
     #[allow(clippy::too_many_arguments)]
-    pub fn process_loop(
+    fn process_loop(
         my_pubkey: Pubkey,
         verified_receiver: &CrossbeamReceiver<Vec<Packets>>,
         poh_recorder: &Arc<Mutex<PohRecorder>>,
@@ -1272,7 +1272,7 @@ impl BankingStage {
 
     #[allow(clippy::too_many_arguments)]
     /// Process the incoming packets
-    pub fn process_packets(
+    fn process_packets(
         my_pubkey: &Pubkey,
         verified_receiver: &CrossbeamReceiver<Vec<Packets>>,
         poh: &Arc<Mutex<PohRecorder>>,