[number field] Make START_AUTO_CHANGE_DELAY Configurable for NumberField

# Feature request

## Summary

I'm using the NumberField component as a quantity input in a shopping cart.
To avoid sending too many HTTP requests, I use a debounce of 200ms on value change.

## Examples in other libraries

## Motivation

Problem:
The component’s built-in `START_AUTO_CHANGE_DELAY` is fixed at 400ms.
So when a user holds down the increment button:

At 200ms: debounce triggers an HTTP request (from the initial increment)

At 400ms: auto-repeat starts, causing a second value change → another HTTP request

This leads to two requests even though the user only held the button once.

Proposal:
Allow START_AUTO_CHANGE_DELAY to be set via props, so it can be aligned with external debounce timing.

Example API:

```tsx

```

Current Workaround:
Set the debounce timeout to >= 400ms, however this introduces a less responsive UX and feels laggy.