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/r681_slice_field_distinct_bytes/case.ww

@@ -0,0 +1,12 @@
+//ww:run-exit 42
+package main;
+type bs = struct { rbuf: []u8, mark: i32 };
+fn main() i32 = {
+	let raw: [16]u8;
+	raw[0] = 0xAAu8; raw[1] = 0xBBu8; raw[2] = 0xCCu8;
+	raw[3] = 0xDDu8; raw[4] = 0xEEu8; raw[5] = 0xFFu8;
+	let b: bs; b.mark = 0x33; b.rbuf = raw[0:6];
+	if (b.rbuf.len != 6) { return 1; }; if (b.rbuf.cap != 16) { return 2; };
+	if (b.mark != 0x33) { return 3; }; if (b.rbuf[0] != 0xAAu8) { return 4; };
+	if (b.rbuf[5] != 0xFFu8) { return 5; }; return 42;
+};