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/r812_assign_48b/case.ww

@@ -0,0 +1,4 @@
+//ww:run-exit 21
+package main;
+type big = struct { a: size, b: size, c: size, d: size, e: size, f: size };
+export fn main() i32 = { let x: big = big { a = 1: size, b = 2: size, c = 3: size, d = 4: size, e = 5: size, f = 6: size }; let y: big = big { a = 0: size, b = 0: size, c = 0: size, d = 0: size, e = 0: size, f = 0: size }; y = x; return (y.a + y.b + y.c + y.d + y.e + y.f): i32; };