allow embedding external content on dashboards (#47994)

* embed cards

* safety

* rename params

* review, renaming

* min and default size of iframe cards

* move ml auto to parent

* use truncate

* spec failures

* empty state

* consistent iFrame copy

* renaming, no fe tracking

* iframe copy

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Co-authored-by: Aleksandr Lesnenko <alxnddr@gmail.com>
Co-authored-by: Aleksandr Lesnenko <alxnddr@users.noreply.github.com>