Replace handler hook with element_id based approach

[eliknebel]

Removes the handler hook API and replaces it with a more transparent and simpler (at least, from the developer API perspective) element_id-based tracking system. The intent here is to keep the optimization where event ids remain stable across updates even though event handler callback functions may be recreated and re-bound on every render cycle, preventing unnecessary id changes in patches for event handlers.

This work achieves that by adding a stable element_id to the ReconciledElement record and utilizing the existing reconciler diffing logic to determine if an element is the same element as the previous element or if it is a new element that needs a new element_id.

With this new approach, it is no longer necessary for a developer to use hooks to define event handlers and event handling should be much simpler. For example, previously a component would need to be written as such:

fn button_component(ctx: Context, _props) {
  use ctx, count, set_count <- state(ctx, 0)

  // Define event handlers
  use ctx, increment <- handler(ctx, fn(_) { set_count(count + 1) })
  use ctx, reset <- handler(ctx, fn(_) { set_count(0) })

  let current_count = int.to_string(count)

  component.render(
    ctx,
    fragment([
      text("current count is: " <> current_count),
      button([id("increment"), events.on_click(increment)], [
        text("increment"),
      ]),
      button([id("reset"), events.on_click(reset)], [text("reset")]),
    ]),
  )
}

Now with these changes, the component handlers can simply be written as normal functions:

fn button_component(ctx: Context, _props) {
  use ctx, count, set_count <- state(ctx, 0)

  // Define event handlers
  let increment = fn(_) { set_count(count + 1) }
  let reset = fn(_) { set_count(0) }

  let current_count = int.to_string(count)

  component.render(
    ctx,
    fragment([
      text("current count is: " <> current_count),
      button([id("increment"), events.on_click(increment)], [text("increment")]),
      button([id("reset"), events.on_click(reset)], [text("reset")]),
    ]),
  )
}

Or with the handler callback inlined with the markup for simple cases:

fn button_component(ctx: Context, _props) {
  use ctx, count, set_count <- state(ctx, 0)

  let current_count = int.to_string(count)

  component.render(
    ctx,
    fragment([
      text("current count is: " <> current_count),
      button(
        [id("increment"), events.on_click(fn(_) { set_count(count + 1) })],
        [text("increment")],
      ),
      button([id("reset"), events.on_click(fn(_) { set_count(0) })], [
        text("reset"),
      ]),
    ]),
  )
}