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_fnptr_indirect/case.ww

@@ -0,0 +1,8 @@
+//ww:run-exit 42
+// Migrated from 700_e2e row 10.
+package main;
+fn add(a: i32, b: i32) i32 = { return a + b; };
+fn main() i32 = {
+  let fp: fn(a: i32, b: i32) i32 = add;
+  return fp(20, 22);
+};