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/r71_struct_field_index_struct_stride/case.ww

@@ -0,0 +1,16 @@
+//ww:run-exit 22
+package main;
+type S = struct { a: i32, b: str };
+fn main() i32 = {
+	let buf: [3]S;
+	buf[0].a = 10i32; buf[0].b = "x";
+	buf[1].a = 22i32; buf[1].b = "yy";
+	buf[2].a = 30i32; buf[2].b = "zzz";
+	let xs: []S;
+	xs.ptr = &buf[0];
+	xs.len = 3;
+	xs.cap = 3;
+	let p: *[]S = &xs;
+	let q: *S = &p.ptr[1];
+	return q.a;
+};