Add wrapper over sled tree to count items (used for big queues)

src/table/gc.rs

@@ -14,6 +14,7 @@ use tokio::sync::watch;
 
 use garage_util::data::*;
 use garage_util::error::*;
+use garage_util::sled_counter::SledCountedTree;
 use garage_util::time::*;
 
 use garage_rpc::system::System;
@@ -362,7 +363,7 @@ impl GcTodoEntry {
 	}
 
 	/// Saves the GcTodoEntry in the gc_todo tree
-	pub(crate) fn save(&self, gc_todo_tree: &sled::Tree) -> Result<(), Error> {
+	pub(crate) fn save(&self, gc_todo_tree: &SledCountedTree) -> Result<(), Error> {
 		gc_todo_tree.insert(self.todo_table_key(), self.value_hash.as_slice())?;
 		Ok(())
 	}
@@ -372,7 +373,7 @@ impl GcTodoEntry {
 	/// This is usefull to remove a todo entry only under the condition
 	/// that it has not changed since the time it was read, i.e.
 	/// what we have to do is still the same
-	pub(crate) fn remove_if_equal(&self, gc_todo_tree: &sled::Tree) -> Result<(), Error> {
+	pub(crate) fn remove_if_equal(&self, gc_todo_tree: &SledCountedTree) -> Result<(), Error> {
 		let _ = gc_todo_tree.compare_and_swap::<_, _, Vec<u8>>(
 			&self.todo_table_key()[..],
 			Some(self.value_hash),