feat(selectors): attribute selectors pierce open shadow roots

[dgozman]

References #1375.

[pavelfeldman]

Confirming that this is not going to help with the list if I'm reaching for an element in the shadow.

[thernstig]

@dgozman @pavelfeldman Shouldn't the selector name be amended/updated with regards updated name attribute? E.g.:

const handle = await page.$('attribute=some-attribute');

[dgozman]

@dgozman @pavelfeldman Shouldn't the selector name be amended/updated with regards updated name attribute? E.g.:

const handle = await page.$('attribute=some-attribute');

The name did not change, we still expose some predefined selectors like id=foo. They are just implemented as attribute selectors.

[thernstig]

Understand, maybe it is a separate issue. I just think it is confusing to call it id when it selects attributes.