Form media given as html-safe strings rendered as paths on 6.1

[Adam Johnson]

Since #29490 (Django 4.1), Media assets may be given as hashable objects implementing __html__(), rendered verbatim as the complete tag, per the old ​"Paths as objects" docs section.
Html-safe strings from mark_safe() satisfy that contract, but since 8096b5251090bf7539c59956e398b027c7525529 (#37085) they are treated as static file paths instead: Media.__init__() now normalizes every isinstance(path, str) entry into Script/Stylesheet, and SafeString is a str subclass, so e.g. forms.Media(js=[mark_safe('<script defer src="https://example.org/asset.js"></script>')])
renders as<script src="/static/%3Cscript%20defer%20src%3D%22https%3A/..."></script> rather than the tag verbatim as in 6.0. The same happens for css entries but non-str @html_safe classes still work.

The fix is to skip normalization for any string that provides __html__(), so that they take the pre-existing verbatim rendering branch.