A potential bug: Some leaves are MISSED when we LOAD StandardIndexedTree

[coldstar1993]

issue code:
https://github.com/AztecProtocol/aztec-packages/blob/4a1e9c32b1aae52811e348d67cab468cdab89bd6/yarn-project/merkle-tree/src/standard_indexed_tree/standard_indexed_tree.ts#L245C47-L245C76

gte, lte are compared by characters (numbers) in the ASCII character set. So here is a potential bug that it would miss some Leaf when loadTree.
For example: When we load from levelDB a tree called NULLIFIER_TREE of height 16 (i.e, 2n ** BigInt(this.getDepth()) = 65536), the runtime code is as below:

this.db
        .createReadStream({
           gte: 'NULLIFIER_TREE:LEAF:0'
           lte: 'NULLIFIER_TREE:LEAF:65536'
         });

then, you could find that many leaves whose key starts with 'NULLIFIER_TREE:LEAF:7'/'NULLIFIER_TREE:LEAF:8'/'NULLIFIER_TREE:LEAF:9' will be missed.