Not easy to get the number of methods llhttp has #872

In aiohttp, we need to create an array of all the method names that llhttp supports for caching purposes.

The problem is that llhttp_method_name abort()s on an out-of-range id (api.c:222), our old code therefore just had a hardcoded constant set to 46 and iterated over them. But, this means when llhttp added the QUERY method, our code didn't pick it up.

Would it be reasonable to add something to llhttp to trivially get this information? Either allowing llhttp_method_name to return NULL rather than abort(), or adding a constant that tells us how many methods are available.

Without something like that, I've had to add this awkward thing to extract the names directly:
https://github.com/aio-libs/aiohttp/pull/13174/changes#diff-061b5abe803b659aa544700e4065e1fbff6e83112315e345ea2d2e31ad1d6ca7R106-R117