DefaultTransactionQueue: Ensure at most 2^12 created notes per batch

[plafer]

Related: #64

[hackaugusto]

@plafer @bobbinth what is suppose to be achieved by this issue? The linked PR seems to talk about how to define the note's leaves, and to define it "using a tree of depth 20" which is kinda unrelated to the issue title.

[bobbinth]

I think this may be as simple as making sure that if batch builder gets a list of more than $n$ transactions (i.e. here, it would return an error. $n$ should probably be defined in miden-base (i.e., here). We could call it MAX_TRANSACTIONS_PER_BATCH and it would be computed based on NOTE_TREE_DEPTH.

[bobbinth]

We could call it MAX_TRANSACTIONS_PER_BATCH and it would be computed based on NOTE_TREE_DEPTH.

Actually, we need one more constant to support this: MAX_BATCHES_PER_BLOCK. Then, MAX_TRANSACTIONS_PER_BATCH is defined as 2.pow(NOTE_TREE_DEPTH - MAX_BATCHES_PER_BLOCK.ilog2()).