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_struct_byval_mixed/case.ww

@@ -0,0 +1,12 @@
+//ww:run-exit 60
+package main;
+type two = struct { sec: i64, nsec: i64 };
+type one = struct { v: i64 };
+fn sum(a: two, b: one) i32 = {
+	return (a.sec + a.nsec + b.v): i32;
+};
+fn main() i32 = {
+	let x: two = two { sec = 10i64, nsec = 20i64 };
+	let y: one = one { v = 30i64 };
+	return sum(x, y);
+};