Combine uri + rawuri into single struct.
Try to improve ownership around URIs and URI-like things.
- cookie & request can take *const std.Uri
(TODO: make them aware of the new URL struct?)
- Location (web api) should own its URL (web api URL)
- Window should own its Location
Most of these changes result in (a) a cleaner Page and (b) not having to carry
around 2 nullable objects (URI and rawuri).
Leverage comptime fields to give generated Tuple a default value, allowing
TupleT and Tuple to be merged.
Only call generate.Tuple on the final output. This eliminates redundant
deduplication, and results in a simpler API (nested types just need to expose
a natural Zig tuple).
generate.Union leverages the new Tuple and removes unused features.
