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/r989_m1union_all_arms/case.ww

@@ -0,0 +1,25 @@
+//ww:run-exit 219
+package main;
+import encoding.utf8;
+fn classify(d: *utf8.decoder) int = {
+	match (utf8.next(d)) {
+	case let r: rune => return 1;
+	case let dn: utf8.done => return 2;
+	case let m: utf8.more => return 3;
+	case let e: utf8.invalid => return 4;
+	};
+	return 0;
+};
+export fn main() int = {
+	let g: []u8 = [65u8];
+	let dg = utf8.decode(g);
+	let a = classify(&dg);
+	let b = classify(&dg);
+	let bad: []u8 = [255u8];
+	let db = utf8.decode(bad);
+	let c = classify(&db);
+	let tr: []u8 = [195u8];
+	let dt = utf8.decode(tr);
+	let e = classify(&dt);
+	return a * 1000 + b * 100 + c * 10 + e;
+};