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/r767_match_variant_nullable_fn/case.ww

@@ -0,0 +1,15 @@
+//ww:run-exit 107
+package main;
+fn ai(x: i32) i32 = { return x + 1; };
+fn bi(x: i32) i32 = { return x + 100; };
+fn indi(f: *fn(x: i32) i32, x: i32) i32 = { return (*f)(x); };
+export fn main() i32 = {
+	let pick: i32 = 1;
+	let v: (*fn(x: i32) i32 | void) = &ai;
+	if (pick != 0) { v = &bi; };
+	let r: i32 = match (v) {
+	case void => yield 99: i32;
+	case let f: *fn(x: i32) i32 => yield indi(f, 7);
+	};
+	return r;
+};