[Feature]: option to remove a locator handler

[DetachHead]

🚀 Feature Request

it would be nice if handlers added by addLocatorHandler could be removed

Example

remove a handler at a certain point in the test:

const handler = await page.addLocatorHandler(page.getByText('Sign up to the newsletter'), async () => {
  await page.getByRole('button', { name: 'No thanks' }).click();
});

await page.goto('https://example.com');
await page.getByRole('button', { name: 'Start here' }).click();

// at this point we can be confident that the popup has either already appeared, or won't appear at all,
// so it's safe to remove the handler.
handler.remove() 

remove a handler after it's called once:

await page.addLocatorHandler(page.getByText('Sign up to the newsletter'), async (handler) => {
  await page.getByRole('button', { name: 'No thanks' }).click();
  handler.remove()
});

### Motivation

- in some cases, a locator handler is only needed once
- at a certain point in the test, you can often be confident that a handler is no longer needed

[dgozman]

Two options we think of:

• { once: true } for a single-use;
• page.removeLocatorHandler(locator, handler) with the same arguments to remove it.