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_arr_i64_index/case.ww

@@ -0,0 +1,11 @@
+//ww:run-exit 100
+// Migrated from 700_e2e row 22.
+package main;
+fn main() i32 = {
+  let arr: [4]i64;
+  arr[0] = 10; arr[1] = 20; arr[2] = 30; arr[3] = 40;
+  let sum: i64 = 0;
+  let i: i32 = 0;
+  for (i < 4) { sum += arr[i]; i += 1; };
+  return sum: i32;
+};