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/r693_dot_plain_slice_ptr/case.ww

@@ -0,0 +1,11 @@
+//ww:run-exit 5
+package main;
+type holder = struct { rbuf: []u8, mark: i32 };
+fn f(h: *holder) i32 = { return h.rbuf.len: i32; };
+fn main() i32 = {
+	let raw: [8]u8;
+	raw[0] = 0u8;
+	let h: holder;
+	h.rbuf = raw[0:5];
+	return f(&h);
+};