test/wcc/data: grow the declarative compiler corpus to 1,224 fixtures

The r-prefixed waves absorb the runtime, reject, and byte-compare rows
of the migrated native carriers; each fixture is one directory with one
case.ww and a //ww:error, //ww:compile, //ww:run, or //ww:run-exit
directive covering both frontends.

test/wcc/data/r823_struct_field/case.ww

@@ -0,0 +1,5 @@
+//ww:run-exit 16
+package main;
+type pt = struct { a: int, b: int };
+let g = pt { a = 7, b = 9 };
+export fn main() i32 = { return (g.a + g.b): i32; };