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/r75_vararg_seq_three_arity_drift/case.ww

@@ -0,0 +1,10 @@
+//ww:run
+package main;
+import os;
+fn pick(args: (str | rune)...) i32 = { return args.len; };
+export fn main() i32 = {
+	if (pick("a") != 1) { os.exit(11); };
+	if (pick("a", "b") != 2) { os.exit(12); };
+	if (pick("a", "b", "c") != 3) { os.exit(13); };
+	return 0;
+};