Optimize `extend_with_marked_digests`

[Francisco Hernández Iglesias]

Using the following optimization for the sync protocol leads to the InvalidUTXOAccumulatorOutput bug. Investigate why and implement the optimization.

/// Appends an iterator of marked leaf digests at the end of the tree, returning the iterator back
    /// if it could not be inserted because the tree has exhausted its capacity.
    ///
    /// # Implementation Note
    ///
    /// This operation is meant to be atomic, so if appending the iterator should fail, the
    /// implementation must ensure that the tree returns to the same state before the insertion
    /// occured.
    #[inline]
    pub fn extend_with_marked_digests<I>(
        &mut self,
        parameters: &Parameters<C>,
        marked_leaf_digests: I,
    ) -> Result<(), I::IntoIter>
    where
        I: IntoIterator<Item = (bool, LeafDigest<C>)>,
        L: Default,
        M: Default,
        InnerDigest<C>: Clone + Default + PartialEq,
        LeafDigest<C>: Clone + Default,
    {
        let marked_leaf_digests = marked_leaf_digests.into_iter();
        if matches!(marked_leaf_digests.size_hint().1, Some(max) if max <= capacity::<C, _>() - self.len())
        {
            let mut marked_inserts = Vec::new();
            for (marking, leaf_digest) in marked_leaf_digests {
                println!("{:?}", marking);
                if marking {
                    marked_inserts.push(leaf_digest);
                } else {
                    if !marked_inserts.is_empty() {
                        println!("Marked inserts length: {:?}", marked_inserts.len());
                        assert!(self.batch_push_digest(parameters, || marked_inserts.drain(..).collect::<Vec<_>>()),
                            "Pushing a leaf digest into the tree should always succeed because of the check above.");
                        println!("Marked inserts length: {:?}", marked_inserts.len());
                    }
                    assert!(self.push_provable_digest(parameters, move || leaf_digest),
                 "Pushing a leaf digest into the tree should always succeed because of the check above.");
                }
            }
            if !marked_inserts.is_empty() {
                assert!(self.batch_push_digest(parameters, || marked_inserts.drain(..).collect::<Vec<_>>()),
                    "Pushing a leaf digest into the tree should always succeed because of the check above.");
            }
            return Ok(());
        }
        Err(marked_leaf_digests)
    }
    ```