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_for_range/case.ww

@@ -0,0 +1,12 @@
+//ww:run-exit 100
+// Migrated from 700_e2e row 35.
+package main;
+import os;
+fn main() i32 = {
+  let s: []u8;
+  s.ptr = nil; s.len = 0; s.cap = 0;
+  append(s, 10u8, 20u8, 30u8, 40u8);
+  let total: i32 = 0;
+  for (let b .. s) { total += b: i32; };
+  return total;
+};