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/r650_u8_leaf/case.ww

@@ -0,0 +1,5 @@
+//ww:run-exit 99
+package main;
+type holder = struct { val: u8, pad: u8 };
+type box = struct { h: holder, tag: i32 };
+fn main() i32 = { let b: box; b.h.val = 99u8; b.h.pad = 0u8; b.tag = 0; return b.h.val: i32; };