Replace the frontend-facing Vector<String> flow with structured
AutocompleteSuggestion objects carrying source, section, title,
and favicon metadata.
Build merged history and literal-URL rows in LibWebView, deduplicate
equivalent URL suggestions, move the autocomplete URL helpers out
of URL.h, and update the history and URL tests around the new model.
The result is currently only used as a StringView, but a future commit
will place the result in Web::Clipboard::SystemClipboardRepresentation,
which requires a ByteString (there's no UTF-8 clipboard requirement).
This is to prepare for custom search engines. If we use AK::format, it
would be trivial for a user (or bad actor) to come up with a template
search engine URL that ultimately crashes the browser due to internal
assertions in AK::format. For example:
https://example.com/crash={1}
Rather than coming up with a complicated pre-format validator, let's
just not use AK::format. Custom URLs will signify their template query
parameters with "%s". So we can do the same with our built-in engines.
When it comes time to format the URL, we will do a simple string
replacement.
