test: migrate 700_e2e rows to corpus fixtures; retire the carrier

136 rows migrated, 0 already owned, 3 wwstage-failing rows held out.

test/wcc/data/r700_alloc_free_assert/case.ww

@@ -0,0 +1,13 @@
+//ww:run-exit 42
+// Migrated from 700_e2e row 45.
+package main;
+import os;
+import rt;
+type point = struct { x: i64, y: i64 };
+fn main() i32 = {
+  let p: *point = alloc(point { x = 7, y = 35 })!;
+  let r: i64 = p.x + p.y;
+  free(p);
+  assert(r == 42, "sum mismatch\n");
+  return r: i32;
+};