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/r820_let_zero_overfill/case.ww

@@ -0,0 +1,4 @@
+//ww:error "array literal has"
+package main;
+let X: [0]int = [1, 2];
+export fn main() i32 = { return X[1]: i32; };