feat: add operator.list support for OCaml binding

[Young-Flash]

just new to OCaml, appericiate for any review suggestion

cc #2756

[PsiACE]

cc @Ranxy , are you interested in reviewing this PR?

[Ranxy]

It seems that the test will fail to run on my machine. After adding the printer, I found the following error

File "test/test.ml", line 97, characters 1-1:
Error: suite:6:test_list (in the code).

expected: [bar; foo] but got: [foo; bar]

It seems that this is a problem with the order of the list results?
I'm not very clear about the specific implementation of the list in opendal rust core, but it seems that the order of the results of the list is different in different platforms, because this test is passed in CI. If so how should the results of the test be sorted?

[Xuanwo]

LGTM. But I'm not familiar with OCaml. Let's wait for @Ranxy's review.