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/r670_i64_7args_signed/case.ww

@@ -0,0 +1,4 @@
+//ww:run-exit 42
+package main;
+fn s7(a: i64, b: i64, c: i64, d: i64, e: i64, f: i64, g: i64) i64 = { return a + b + c + d + e + f + g; };
+fn main() i32 = { let r: i64 = s7(-1i64, -2i64, -3i64, -4i64, -5i64, -6i64, 49i64); if (r == 28i64) { return 42; }; return 0; };