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/r691_ptr_root_slice_mutate_ptr/case.ww

@@ -0,0 +1,9 @@
+//ww:run-exit 42
+package main;
+type outer = struct { sl: []u8, x: i32 };
+fn poke(s: []u8) void = { s[0] = 0x42u8; };
+fn main() i32 = {
+	let arr: [8]u8; arr[0] = 0u8; let o: outer;
+	o.sl.ptr = &arr[0]; o.sl.len = 1; o.sl.cap = 8; let p: *outer = &o;
+	poke(p.sl); if (arr[0]: i32 != 0x42) { return 1; }; return 42;
+};