Fix generated wrapper for nested struct with static fn, rebase and fix of original PR

[qthree]

Based on #1380
Original PR generated invalid code, I've made corrections, now integration_tests are passing locally, except for:

• integration_test::test_string_in_struct
• integration_test::test_typedef_to_up_in_fn_call
• integration_test::test_typedef_to_up_in_struct
• integration_test::test_up_in_struct
  but they don't pass on main branch either.

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