Move logic calculating the index in Vector.at to a builtin method to make the performance of Vector to be on par with Array

[hubertp]

Pull Request Description

The main culprit of a Vector slowdown (when compared to Array) was the normalization of the index when accessing the elements. Turns out that the Graal was very persistent on not inlining that particular fragment and that was degrading the results in benchmarks.

Being unable to force it to do it (looks like a combination of thunk execution and another layer of indirection) we resorted to just moving the normalization to the builtin method. That makes Array and Vector perform roughly the same.

Moved all handling of invalid index into the builtin as well, simplifying the Enso implementation. This also meant that Vector.unsafe_at is now obsolete.
Additionally, added support for negative indices in Array, to behave in the same way as for Vector.

Important Notes

Note that this workaround only addresses this particular perf issue. I'm pretty sure we will have more of such scenarios.
Before the change averageOverVector benchmark averaged around 0.033 ms/op now it does consistently 0.016 ms/op, similarly to averageOverArray.

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the
  Scala,
  Java,
  and
  Rust
  style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH
    ./run ide build and ./run ide watch.

[JaroslavTulach]

I'd suggest to remove Vector.unsafe_at, now when Vector.at is fast enough.

[JaroslavTulach]

Please make sure Array.at behaves the same as Vector.at - e.g. it can also handle negative indexes.

[radeusgd]

I like that Arrays now fail with dataflow errors as vectors - the consistency is cool.

Also really appreciating how easy and clean it is now to add a builtin type!

[hubertp]

I also added some documentation to explain how I figured that (and others) out.

[JaroslavTulach]

;-)

[hubertp]

To put it mildly.