Ajax: Make responseJSON work for erroneous same-domain JSONP requests

Ajax: Make responseJSON work for erroneous same-domain JSONP requests

Don't use a script tag for JSONP requests unless for cross-domain requests
or if scriptAttrs are provided. This makes the `responseJSON` property available
in JSONP error callbacks.

This fixes a regression from jQuery 3.5.0 introduced in gh-4379 which made
erroneous script responses to not be executed to follow native behavior.

The 3.x-stable branch doesn't need this fix as it doesn't use script tags for
regular async requests.

Closes gh-4778
Ref gh-4771
Ref gh-4773
Ref gh-4379