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_enum_cross_module/case.ww

@@ -0,0 +1,12 @@
+//ww:run-exit 42
+// Migrated from 700_e2e row 123.
+package pkg;
+export type base = enum i32 { DEC = 10, HEX = 16 };
+package main;
+import pkg;
+fn pick(b: pkg.base) i32 = { return b as i32; };
+fn main() i32 = {
+  let a: i32 = pick(pkg.base.DEC);
+  let b: i32 = pick(pkg.base.HEX);
+  return a + b + 16;
+};