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/r703_nested_middle/case.ww

@@ -0,0 +1,4 @@
+//ww:run-exit 153
+package main;
+type inner = struct { a: i64, b: i64 }; type outer = struct { pre: i64, i: inner, post: i64 };
+fn main() i32 = { let o: outer = outer { pre = 100i64, i = inner { a = 1i64, b = 2i64 }, post = 50i64 }; return (o.pre + o.i.a + o.i.b + o.post): i32; };