Fixmmr part2 (#3666)

* use 0-based positions in  methods pmmr_leaf_to_insertion_index and bintree_postorder_height; add round_up_to_leaf_pos method

* use 0-based positions in method insertion_to_pmmr_index

* use 0-based positions in method is_leaf

* use 0-based positions in method family()

* use 0-based positions in method is_left_sibling

* use 0-based positions in method family_branch

* use 0-based positions in methods bintree_{left,right}most

* use 0-based positions in method bintree_pos_iter

* use 0-based positions in method bintree_range

* use 0-based positions in method bintree_leaf_pos_iter

* rename last_pos in MMR related structs to size

* use 0-based positions in method prune

* use 0-based positions in method push and apply_output return value

* use 0-based position argument of method merkle_proof

* use 0-based outputs in method pmmr::peaks

* fix peaks() code comments

* refix peaks() code comments

* use 0-based positions in method get_peak_from_file

* use 0-based positions in methods get_data_from_file

* use 0-based positions in methods get_from_file

* use 0-based positions in methods get_data

* use 0-based positions in methods get_hash

* use 0-based positions in method peak_path

* use 0-based positions in method bag_the_rhs

* use 0-based positions in method Backend::remove

* use 0-based positions in method leaf_pos_iter

* use 0-based positions in method self.LeafSet::includes

* use 0-based positions in methods self.LeafSet::{add,remove}

* use 0-based positions in methods is_pruned,is_pruned_root,is_compacted

* use 0-based positions in methods PruneList::append

* use 0-based positions in methods append_pruned_subtree

* use 0-based positions in method calculate_next_leaf_shift

* use 0-based positions in method append_single

* use 0-based positions in method calculate_next_shift

* use 0-based positions in method segment_pos_range

* use 0-based positions in method reconstruct_root

* use 0-based positions in method validate_with

* use 0-based positions in method validate

* rename size (formerly last_pos) to mmr_size

* use 0-based positions in Segment's hash_pos and leaf_pos

* minimize use of saturating_sub(1) and rename some pos/idx to size

* use 0-based positions in methods get_output_pos

* use 0-based positions in method get_unspent_output_at

* use 0-based positions in method get_header_hash

* use 0-based positions in methods MerkleProof::verify{,_consume}

* use 0-based positions in method cleanup_subtree

* don't allow 0 in prunelist bitmap

* use 0-based positions in methods get_{,leaf_}shift

* rename some 1-based pos to pos1; identify TODO

* Address yeastplume's PR review comments

api/src/handlers/utils.rs

@@ -71,7 +71,7 @@ pub fn get_output_v2(
 		None => return Ok(None),
 	};
 
-	let output = chain.get_unspent_output_at(pos.pos)?;
+	let output = chain.get_unspent_output_at(pos.pos - 1)?;
 	let header = if include_merkle_proof && output.is_coinbase() {
 		chain.get_header_by_height(pos.height).ok()
 	} else {