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_chain3_ptrfield/case.ww

@@ -0,0 +1,13 @@
+//ww:run-exit 99
+// Migrated from 700_e2e row 110.
+package main;
+type leaf = struct { v: i32 };
+type mid  = struct { l: *leaf };
+type top  = struct { m: *mid };
+fn main() i32 = {
+  let lf: leaf = leaf { v = 0 };
+  let md: mid  = mid  { l = &lf };
+  let tp: top  = top  { m = &md };
+  tp.m.l.v = 99;
+  return tp.m.l.v;
+};