(many) Add implicitly typed int arrays

[perlun]

This is an important step towards completing #487, but a few more things are needed for this:

• Being able to specify int[] as an explicit type specifier. Right now, only implicitly typed int arrays are supported.
• Being able to use this for other data types like long[], double[] and string[].

As for the underlying perlang::IntArray class, what I am aiming for here is something a bit more high-level than traditional C-style int[] arrays. They are nice in the sense of being "low overhead" but are also prone to all kinds of C-style memory issues (heap overflow, most notably). Perlang arrays will be more akin to Java or C#-style arrays, which are inherently "safe by design". It should be more or less impossible to use a Perlang array in such a way as to cause the program to crash. Because we don't have a JVM or MSIL interpreter to help us with this, we have to implement the boundary checks on our own.

At the moment, those boundary checks throw (C++) exceptions. We could consider adding more "try"-oriented methods too, like try_get(index, default_value) or even try_get(index, () -> default_value) if we want to be more fancy. Either way, the point is to avoid exceptions and let the caller (by returning a bool) check if the operation was successful or not by different, sometimes more appropriate means than exceptions.

[perlun]

Hmm, would have been nice to take in the same PR I guess. 🙈 Will have to come in a followup PR.

[perlun]

Taken care of here now: https://github.com/perlang-org/perlang/pull/496/files#r1644983171