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/r800append_str_len_bytes/case.ww

@@ -0,0 +1,8 @@
+//ww:run-exit 11
+package main;
+export fn main() i32 = {
+	let xs: []str = [];
+	let s: str = "abcdef";
+	append(xs, s);
+	return (xs[0].len: i32) + (xs[0][5]: i32) - (xs[0][0]: i32);
+};