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/r926_sret_reject_widen_forward/case.ww

@@ -0,0 +1,16 @@
+//ww:error "widening tagged return-forward"
+package main;
+type oops = !str;
+type nomem = !void;
+type wide = struct { xs: []u8, ys: []u8, n: i64 };
+fn inner(b: []u8) (wide | oops) = { return wide { xs = b, ys = b, n = 1 }; };
+fn outer(b: []u8) (wide | oops | nomem) = { return inner(b); };
+export fn main() i32 = {
+	let buf: [4]u8 = [1u8, 2u8, 3u8, 4u8];
+	match (outer(buf[0:4])) {
+	case let w: wide => return 0;
+	case let e: oops => return 13;
+	case nomem => return 14;
+	};
+	return 0;
+};