Fix issue with ordering of module opened via -open

[zth]

This fixes a very annoying issue where you wouldn't get autocomplete for "second order opens". I haven't added any tests because it'd be an incredibly noisy diff, but here's roughly what was wrong and what it caused:

1. Say you have an open in bsc-flags, like -open RescriptCore. Everything works as expected
2. The RescriptCore open exposes a bunch of modules like Array, List, Result etc. All of these are available in autocomplete. So far, so good.
3. Now, let's say you were to add an explicit open in a file for a module exposed via -open RescriptCore, like open Array.
4. The content of Array won't be exposed to autocomplete in this case.

As can be seen by the minimal diff, this was a case of ordering. The list is reversed (correctly), but the order of rawOpens (coming from the local file) and packageOpens (coming from the package, bsconfig/rescript.json) was off, so the package opens actually ended up after the local opens when resolving autocomplete. This in turn lead to the contents of the opened modules not being exposed.

Phew.

[cristianoc]

Seems legit.