- Add anyascii to replace unidecode
- Update wagtail.core.utils.string_to_ascii to use anyascii.
- Anyascii has a similar but not exactly the same encoding - see updates to tests.
Refs https://github.com/wagtail/wagtail/issues/3311
Fixes #6288
Many of the oembed endpoints currently listed with an http:// URL now redirect to https://. Changing these to https:// saves a redundant redirect and avoids failures where the http URL has been blocked (see #6288). Also simplified the patterns for matching http or https - the group in `http(?:s)?` is redundant and should just be `https?`.
