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_switch_multi/case.ww

@@ -0,0 +1,14 @@
+//ww:run-exit 159
+// Migrated from 700_e2e row 24.
+package main;
+fn classify(x: i32) i32 = {
+  switch (x) {
+    case 1, 2, 3: return 10;
+    case 10: return 99;
+    case: return 50;
+  };
+  return -1;
+};
+fn main() i32 = {
+  return classify(2) + classify(10) + classify(99);
+};