E2EElement is missing removeAttribute()/toggleAttribute()

[jcfranco]

Stencil version:

 @stencil/core@one

I'm submitting a:

[ ] bug report
[x] feature request
[ ] support request => Please do not submit support requests here, use one of these channels: https://stencil-worldwide.herokuapp.com/ or https://forum.ionicframework.com/

Current behavior:

There is no way to remove boolean attributes with the existing E2EElement APIs. This is particularly problematic if your test involves a native element that has a boolean attribute that is not reflected via its matching property (e.g., input#checked).

Expected behavior:

E2EElement should provide the necessary APIs for the following type of test:

it("should react when input#checked changes", async () => {
  const page = await newE2EPage();
  await page.setContent(
    "<my-component><input type='radio' slot='radio' value='1' checked></my-component>"
  );

  const element = await page.find("my-component");
  const radio = await page.find("my-component >>> input[slot=radio]");

  let checked = await element.getProperty("checked");
  expect(checked).toBeTruthy();

  radio.removeAttribute("checked"); // or toggleAttribute

  checked = await element.getProperty("checked");
  expect(checked).toBeFalsy();
});

Steps to reproduce:

See ☝️.

Related code:

See ☝️.

Other information:

N/A