Make Blockstore::get_slots_since() filter out results for dead slots

[steviez]

Problem

This function is used by ReplayStage to find new slots to replay. If we know the slot is dead, then we can ignore the slot instead of creating the bank and later finding out that it is dead.

Moreso, if the slot was processed in validator startup processing (blockstore_processor::load_frozen_forks()) and then also processed by ReplayStage, we will have created a bank for that slot twice, which causes a downchain failure.

Summary of Changes

Filter out dead slots from Blockstore::get_slots_since().

Fixes #28343

[steviez]

Think this one needs to go in v1.14 and v1.13/v1.10

[jeffwashington]

cf = column family?

[jeffwashington]

alive_slots is already a vec. is this required to clone it?

[jeffwashington]

you can get rid of this

[jeffwashington]

u64 could be Slot for clarity and consistency.

[jeffwashington]

lgtm. @carllin should review the meaning/concept of get_slots_since not returning dead slots for correctness.

[steviez]

Talking with Carl, this solution may not be the safest. I have another idea, but it is a little more involved. Will pursue that

[steviez]

Circling back, this PR is NOT the correct approach to take as this comment calls out

solana/core/src/replay_stage.rs

Lines 1747 to 1749 in 6972afe

	// All errors must lead to marking the slot as dead, otherwise,
	// the `check_slot_agrees_with_cluster()` called by `replay_active_banks()`
	// will break!

and which is later shown here

solana/core/src/cluster_slot_state_verifier.rs

Lines 499 to 515 in 6972afe

	match bank_status {
	BankStatus::Dead | BankStatus::Frozen(_) => (),
	// No action to be taken yet
	BankStatus::Unprocessed => {
	return vec![];
	}
	}
	let bank_hash = bank_status.bank_hash().expect("bank hash must exist");
	let mut state_changes = vec![];
	let is_dead = bank_status.is_dead();
	if is_dead {
	state_changes.push(ResultingStateChange::SendAncestorHashesReplayUpdate(
	AncestorHashesReplayUpdate::DeadDuplicateConfirmed(slot),
	));
	}

ReplayStage needs to know about these dead slots, so changing the function to not return them will definitely break things. Abandoning this PR in lieu of another apporach