[items] ItemPersistence: Add PersistedItem::instant

[florian-h05]

Refs openhab/openhab-core#4384.
Requires openHAB 4.3.0.M3 or newer.

Also provide access to the raw Java types wrapped by PersistedState and PersistedItem.

[florian-h05]

I did some benchmarking, as Java Instant to JS Instant is much faster than Java ZonedDateTime to JS ZonedDateTime,
it seems that calling PersistedItem::instant is by at least factor 10 faster for approx. 1400 states than PersistedState::timestamp:

Running benchmarks for 1477 states ...
Benchmarking Java getTimestamp() ...
Benchmark finshed, took 17 ms
Benchmarking Java getTimestamp() converted to JS-Joda ...
Benchmark finshed, took 965 ms
Benchmarking Java getInstant() ...
Benchmark finshed, took 10 ms
Benchmarking Java getInstant() converted to JS-Joda ...
Benchmark finshed, took 82 ms

Benchmarking Script

var PersistenceExtensions = Java.type('org.openhab.core.persistence.extensions.PersistenceExtensions');
var midnight = time.toZDT('2024-11-01T00:00:00');
var item = items.getItem('Aussentemperatur');
var start, end;

var states = PersistenceExtensions.getAllStatesSince(item.rawItem, midnight);
console.info(`Running benchmarks for ${states.length} states ---------------------------------------------------`)

start = time.Instant.now().toEpochMilli();
console.log('Benchmarking Java getTimestamp() ...')
for (var i = 0; i < states.length; i++) {
  var state = states[i];
  var ts = state.getTimestamp();
}
var end = time.Instant.now().toEpochMilli();
console.log('Benchmark finshed, took ' + (end - start) + ' ms');

start = time.Instant.now().toEpochMilli();
console.log('Benchmarking Java getTimestamp() converted to JS-Joda ...')
for (var i = 0; i < states.length; i++) {
  var state = states[i];
  var ts = time.javaZDTToJsZDT(state.getTimestamp());
}
var end = time.Instant.now().toEpochMilli();
console.log('Benchmark finshed, took ' + (end - start) + ' ms');

start = time.Instant.now().toEpochMilli();
console.log('Benchmarking Java getInstant() ...')
for (var i = 0; i < states.length; i++) {
  var state = states[i];
  var ts = state.getInstant();
}
var end = time.Instant.now().toEpochMilli();
console.log('Benchmark finshed, took ' + (end - start) + ' ms');

start = time.Instant.now().toEpochMilli();
console.log('Benchmarking Java getInstant() converted to JS-Joda ...')
for (var i = 0; i < states.length; i++) {
  var state = states[i];
  var ts = time.javaInstantToJsInstant(state.getInstant());
}
var end = time.Instant.now().toEpochMilli();
console.log('Benchmark finshed, took ' + (end - start) + ' ms');


states = item.persistence.getAllStatesSince(midnight);

start = time.Instant.now().toEpochMilli();
console.log('Benchmarking JS timestamp ...')
for (var i = 0; i < states.length; i++) {
  var state = states[i];
  var ts = state.timestamp;
}
var end = time.Instant.now().toEpochMilli();
console.log('Benchmark finshed, took ' + (end - start) + ' ms');

start = time.Instant.now().toEpochMilli();
console.log('Benchmarking JS instant ...')
for (var i = 0; i < states.length; i++) {
  var state = states[i];
  var ts = state.instant;
}
var end = time.Instant.now().toEpochMilli();
console.log('Benchmark finshed, took ' + (end - start) + ' ms');