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/r71_match_spill_str_payload/case.ww

@@ -0,0 +1,13 @@
+//ww:run-exit 5
+package main;
+fn pick(b: bool) (str | i64) = {
+	if (b) { return "hello"; };
+	return 7i64;
+};
+fn main() i32 = {
+	match (pick(true)) {
+	case let e: i64 => return (e: i32) + 200;
+	case let s: str => return s.len: i32;
+	};
+	return 0;
+};