Adopt heaviest subtree fork choice rule (#10441)

* Add HeaviestSubtreeForkChoice

* Make replay stage switch between two fork choice rules

Co-authored-by: Carl <carl@solana.com>

core/src/fork_choice.rs

@@ -0,0 +1,40 @@
+use crate::{
+    consensus::{ComputedBankState, SwitchForkDecision, Tower},
+    progress_map::ProgressMap,
+    replay_stage::HeaviestForkFailures,
+};
+use solana_ledger::bank_forks::BankForks;
+use solana_runtime::bank::Bank;
+use std::{
+    collections::{HashMap, HashSet},
+    sync::{Arc, RwLock},
+};
+
+pub(crate) struct SelectVoteAndResetForkResult {
+    pub vote_bank: Option<(Arc<Bank>, SwitchForkDecision)>,
+    pub reset_bank: Option<Arc<Bank>>,
+    pub heaviest_fork_failures: Vec<HeaviestForkFailures>,
+}
+
+pub(crate) trait ForkChoice {
+    fn compute_bank_stats(
+        &mut self,
+        bank: &Bank,
+        tower: &Tower,
+        progress: &mut ProgressMap,
+        computed_bank_stats: &ComputedBankState,
+    );
+
+    // Returns:
+    // 1) The heaviest overall bbank
+    // 2) The heavest bank on the same fork as the last vote (doesn't require a
+    // switching proof to vote for)
+    fn select_forks(
+        &self,
+        frozen_banks: &[Arc<Bank>],
+        tower: &Tower,
+        progress: &ProgressMap,
+        ancestors: &HashMap<u64, HashSet<u64>>,
+        bank_forks: &RwLock<BankForks>,
+    ) -> (Arc<Bank>, Option<Arc<Bank>>);
+}