`ctor` doesn't work for ocaml as `staticlib`

I double-checked again. I believe the changes in this PR are correct. However, for reasons we don't know (maybe `ctor` doesn't work in OCaml?), it doesn't work as expected. We can debug the ocaml's bug in another new issue instead.

Can you change OCaml to test against memory instead? We should just change https://github.com/apache/opendal/blob/661e65bb97e56354e7986cdd75b3e01b595d6377/bindings/ocaml/test/test.ml#L29

Some test cases might fail too, so we need to update them accordingly.

_Originally posted by @Xuanwo in https://github.com/apache/opendal/issues/6970#issuecomment-3641456202_

---

Ok, it's actually a Rust bug:

https://github.com/mmastrac/rust-ctor/issues/280
https://github.com/rust-lang/rust/issues/99721

Open bindings/ocaml/test/test.ml at line 29 and inspect how the OCaml test currently checks ctor behavior. Run the relevant OCaml tests to identify affected cases, then change the check to use memory and update any failing cases so the test suite passes.

Written by the indexing model from the issue text.