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/r690_amp_dot_slice_len_writethrough/case.ww

@@ -0,0 +1,8 @@
+//ww:run-exit 0
+package main;
+fn main() i32 = {
+	let arr: [4]u8; let s: []u8;
+	s.ptr = &arr[0]; s.len = 4; s.cap = 4;
+	let q: *i64 = &s.len; *q = 0i64;
+	return s.len: i32;
+};