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/r831_match_field_remap/case.ww

@@ -0,0 +1,7 @@
+//ww:run-exit 12
+package main;
+type box = struct { t: (int | bool), n: int };
+fn main() i32 = {
+	let b: box = box { t = true, n = 5 }; b.t = 7;
+	match (b.t) { case let n: int => return (n + b.n): i32; case bool => return 1; };
+};