chore: update escrow to use PrivateImmutable

[nventuro]

Working on #4940 I found that this contract uses PrivateSet (aka Set), when PrivateImmutable would actually be a much better fit. The escrow was reading set notes without nullifying them because it doesn't ever remove notes from the set (and hence all notes that were ever created are always valid). This can be very confusing for a beginner, and was a bad example to showcase.

I also removed the docs decorators since we don't ever reference them.

[AztecBot]

Benchmark results

Metrics with a significant change:

• note_history_successful_decrypting_time_in_ms (5): 1,366 (-17%)

Detailed results

All benchmarks are run on txs on the Benchmarking contract on the repository. Each tx consists of a batch call to create_note and increment_balance, which guarantees that each tx has a private call, a nested private call, a public call, and a nested public call, as well as an emitted private note, an unencrypted log, and public storage read and write.

This benchmark source data is available in JSON format on S3 here.

Values are compared against data from master at commit 8ffe5df7 and shown if the difference exceeds 1%.

L2 block published to L1

Each column represents the number of txs on an L2 block published to L1.

Metric	8 txs	32 txs	64 txs
l1_rollup_calldata_size_in_bytes	5,700	18,884	36,452
l1_rollup_calldata_gas	66,048	238,700	469,796
l1_rollup_execution_gas	193,996	500,006	909,054
l2_block_processing_time_in_ms	1,213 (+2%)	4,544 (-2%)	9,021
note_successful_decrypting_time_in_ms	199	552 (+3%)	1,038 (+3%)
note_trial_decrypting_time_in_ms	112	80.6 (+38%)	60.2 (+64%)
l2_block_building_time_in_ms	15,884 (-1%)	63,259 (-1%)	127,065
l2_block_rollup_simulation_time_in_ms	12,087	48,203 (-1%)	96,856
l2_block_public_tx_process_time_in_ms	3,768 (-1%)	14,983 (-1%)	30,050

L2 chain processing

Each column represents the number of blocks on the L2 chain where each block has 16 txs.

Metric	5 blocks	10 blocks
node_history_sync_time_in_ms	14,507 (-5%)	27,513 (-2%)
note_history_successful_decrypting_time_in_ms	⚠️ 1,366 (-17%)	2,385 (-2%)
note_history_trial_decrypting_time_in_ms	100 (-15%)	146 (-9%)
node_database_size_in_bytes	18,796,624	35,582,032 (+1%)
pxe_database_size_in_bytes	29,923	59,478

Circuits stats

Stats on running time and I/O sizes collected for every circuit run across all benchmarks.

Circuit	circuit_simulation_time_in_ms	circuit_input_size_in_bytes	circuit_output_size_in_bytes
private-kernel-init	248 (-1%)	44,736	28,001
private-kernel-ordering	177 (-1%)	52,625	14,627
base-rollup	1,276 (-2%)	177,932	933
root-rollup	70.7 (-1%)	4,192	825
private-kernel-inner	311 (-2%)	73,715	28,001
public-kernel-app-logic	190 (-1%)	32,254	25,379
merge-rollup	5.70 (-2%)	2,712	933

Tree insertion stats

The duration to insert a fixed batch of leaves into each tree type.

Metric	1 leaves	2 leaves	8 leaves	16 leaves	32 leaves	64 leaves	128 leaves	512 leaves	1024 leaves	2048 leaves	4096 leaves
batch_insert_into_append_only_tree_16_depth_ms	9.86	11.1 (+1%)	12.6 (+1%)	16.1 (-2%)	22.5 (-3%)	35.7	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_count	16.9	17.5	23.0	31.6	47.0	79.0	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_16_depth_hash_ms	0.571	0.613 (+1%)	0.534 (+1%)	0.498 (-1%)	0.469 (-4%)	0.443	N/A	N/A	N/A	N/A	N/A
batch_insert_into_append_only_tree_32_depth_ms	N/A	N/A	N/A	N/A	N/A	45.8	72.6	232	443	867 (-4%)	1,738
batch_insert_into_append_only_tree_32_depth_hash_count	N/A	N/A	N/A	N/A	N/A	96.0	159	543	1,055	2,079	4,127
batch_insert_into_append_only_tree_32_depth_hash_ms	N/A	N/A	N/A	N/A	N/A	0.469	0.448	0.421	0.415	0.413 (-4%)	0.415
batch_insert_into_indexed_tree_20_depth_ms	N/A	N/A	N/A	N/A	N/A	54.7 (+1%)	108	343 (+1%)	660	1,313 (-3%)	2,622
batch_insert_into_indexed_tree_20_depth_hash_count	N/A	N/A	N/A	N/A	N/A	104	207	691	1,363	2,707	5,395
batch_insert_into_indexed_tree_20_depth_hash_ms	N/A	N/A	N/A	N/A	N/A	0.480	0.486	0.460	0.453	0.454 (-3%)	0.454
batch_insert_into_indexed_tree_40_depth_ms	N/A	N/A	N/A	N/A	61.3	N/A	N/A	N/A	N/A	N/A	N/A
batch_insert_into_indexed_tree_40_depth_hash_count	N/A	N/A	N/A	N/A	109	N/A	N/A	N/A	N/A	N/A	N/A
batch_insert_into_indexed_tree_40_depth_hash_ms	N/A	N/A	N/A	N/A	0.535	N/A	N/A	N/A	N/A	N/A	N/A

Miscellaneous

Transaction sizes based on how many contracts are deployed in the tx.

Metric	0 deployed contracts
tx_size_in_bytes	19,179

Transaction processing duration by data writes.

Metric	0 new note hashes	1 new note hashes
tx_pxe_processing_time_ms	2,606 (-2%)	1,345 (-1%)

Metric	0 public data writes	1 public data writes
tx_sequencer_processing_time_ms	0.0296 (-2%)	464 (-1%)

[benesjan]

Makes sense 👍