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/r921_amp_xmod_scalar/case.ww

@@ -0,0 +1,7 @@
+//ww:run-exit 42
+package myf;
+export let S: i32 = 42;
+package main;
+import myf;
+fn rd(p: *i32) i32 = { return *p; };
+export fn main() i32 = { return rd(&myf.S); };