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/r681_struct_field_value_write_16b/case.ww

@@ -0,0 +1,11 @@
+//ww:run-exit 42
+package main;
+type inner = struct { a: i64, b: i64 };
+type outer = struct { i: inner, mark: i32 };
+fn main() i32 = {
+	let o: inner; o.a = 0x1122334455667788i64; o.b = 0x99aabbccddeeff00i64;
+	let x: outer; x.mark = 0x55; x.i = o;
+	if (x.i.a != 0x1122334455667788i64) { return 1; };
+	if (x.i.b != 0x99aabbccddeeff00i64) { return 2; };
+	if (x.mark != 0x55) { return 3; }; return 42;
+};