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_ptr_slice_pseudo/case.ww

@@ -0,0 +1,5 @@
+//ww:run-exit 5
+package main;
+type bag = struct { buf: []u8, x: i32 };
+fn setlen(b: *bag, n: i32) void = { b.buf.len = n; };
+fn main() i32 = { let b: bag; let nope: []u8; b.buf = nope; b.x = 0; setlen(&b, 5); return b.buf.len: i32; };