Allow isExisting to work with an composed element

[christian-bromann]

Proposed changes

If you create an element via:

const elem = await browser.$({ 'element-6066-11e4-a52e-4f735466cecf': otherElem.elementId })

WebdriverIO is currently unable to check its existence given that there are no selector information available. As a workaround this patch introduces a fix that uses getElementTagName to check if the element is stale or not.

fixes #7343

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Checklist

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• I have added proper type definitions for new commands (if appropriate)

Further comments

It would be ideal if there would be a way to allow fetching information about the element that allows to refetch it. I don't think this is possible. This should be simplified on protocol level.

Reviewers: @webdriverio/project-committers