Hide API removed in LLVM 17

[QuLogic]

For simplicity, I've kept it all around for users that want to wait on moving to LLVM 17 fully, and just hidden it with build tags.

[aykevl]

I would like to keep the API and the tests the same (as much as possible) between LLVM versions.

Can you:

• Remove APIs that were removed in LLVM (not just hide them with a build tag), for example the ConstSelect function.
• Keep the tests the same, for example by removing the removed passes in executionengine_test.go.

[aykevl]

For simplicity, I've kept it all around for users that want to wait on moving to LLVM 17 fully, and just hidden it with build tags.

In my opinion, people that are not ready to update to LLVM 17 should use an older version of this package that does include those older APIs.
(I'm saying that because the main consumer of go-llvm is TinyGo, and in TinyGo I am not going to use such older APIs when updating the LLVM version unless there is no other way to do something. If there are other users of this package that work differently, this can be reconsidered of course).

[aykevl]

I have merged an alternative to this in #55 so closing. The APIs are now removed entirely, instead of hiding them with a build tag.