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/r807_insert_elem_reject_spread/case.ww

@@ -0,0 +1,3 @@
+//ww:error "insert: spread form insert(xs[i], vs...) unimplemented (task #35)"
+package main;
+export fn main() i32 = { let xs: []u8 = []; let vs: []u8 = []; append(vs, 1u8); insert(xs[0], vs...); return 0; };