This commit is a significant refactor that fixes a number of things.
1. Replaces the optional helpers import (which was always weird) with a
mandatory interface import on behalf of the application. This is
actually a good thing as it enables all things below.
2. Removes the severely awkward union that was the lambda context. Now,
no matter how your handler runs, a single object with everything you
need is fully populated and (nearly always) works as you would
expect. There is a slight exception to this with AWS Lambda that is
related to the service itself. It is also possible that not
everything is passed in correctly for Cloudflare, which, if true,
will be addressed later.
3. Allows writes to the context object. These will be added to the
output, but is implementation dependent, and I'm not 100% sure I've
got it right yet, but the infrastructure is there.
4. Allows proper tests throughout this project.
5. Allows proper tests in the application too.
6. Removes the need for the handler to be public under flexlib. Flexilib
handler registration now works just like everything else. Note,
however, that flexilib is unique in that your handler registration
function will return before the program ends. If this is important
for resource cleanup, @import("build_options").build_type is your
friend.
7. Request method can now be passed into console applications using -m
or --method
