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/r773_spread_is_inline_variant/case.ww

@@ -0,0 +1,12 @@
+//ww:run-exit 3
+// Migrated from 773_isas_spread_variant row spread_is_inline_variant.
+package main;
+import io;
+type rsh = (size | io.eof | ...io.error);
+export fn main() i32 = {
+    let r: rsh = 42: size;
+    if (r is io.underread) { return 1; };
+    if (r is io.eof) { return 2; };
+    if (r is size) { return 3; };
+    return 0;
+};