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/r989_callarg_slice_borrow/case.ww

@@ -0,0 +1,8 @@
+//ww:run
+package main;
+fn takesslice(xs: []int) int = { return len(xs): int; };
+export fn main() int = {
+	let a: [3]int = [1, 2, 3];
+	if (takesslice(a) != 3) { return 1; };
+	return 0;
+};