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_direct_slice_arg_baseline/case.ww

@@ -0,0 +1,11 @@
+//ww:run-exit 42
+package main;
+fn slen(s: []u8) i32 = { return s.len: i32; };
+fn scap(s: []u8) i32 = { return s.cap: i32; };
+fn sfirst(s: []u8) i32 = { return s[0]: i32; };
+fn main() i32 = {
+	let arr: [8]u8; arr[0] = 9u8; let s: []u8;
+	s.ptr = &arr[0]; s.len = 5; s.cap = 8;
+	if (slen(s) != 5) { return 1; }; if (scap(s) != 8) { return 2; };
+	if (sfirst(s) != 9) { return 3; }; return 42;
+};