Add `ECMAScriptRegex`, LibRegex's C++ facade for ECMAScript regexes.
The facade owns compilation, execution, captures, named groups, and
error translation for the Rust backend, which lets callers stop
depending on the legacy parser and matcher types directly. Use it in the
remaining non-LibJS callers: URLPattern, HTML input pattern handling,
and the places in LibHTTP that only needed token validation.
Where a full regex engine was unnecessary, replace those call sites with
direct character checks. Also update focused LibURL, LibHTTP, and WPT
coverage for the migrated callers and corrected surrogate handling.
It turns out that the problem here was simply that we were trimming
trailing whitespace when we did not need to, which was meaning that
the port number of '80 ' was being converted to the empty string
per URLPattern elision as the port matches the http scheme.
This is to save a future name conflict that will appear between
the options IDL dictionary and the options struct that are both
present in the spec.
It is also a nicer interface for now given there is only a single
option at the moment.
This is the core object behind a URL pattern which when constructed
can be used for matching the pattern against URLs.
However, the implementation here is missing key functions such as
the constructor and the 'test'/'exec' functions as that relies on
a significant amount of supporting URLPattern infrastructure such
as two different parsers and a tokenizer.
However, this is enough for us to implement some more of the IDL
wrapper layer of this specification.
