Add keyValueIterator to arrays

[Aurel300]

Closes #871 (and unblocks HaxeFoundation/haxe#7422).

I mostly followed the implementation of iterator for Arrays. Some things that I am not sure about:

• include/hx/Object.h has a clsIdArrayIterator - should there ba a clsIdArrayKeyValueIterator? I couldn't figure out what these clsId things actually do. For now the KV iterator is also marked as clsIdArrayIterator.
• src/cppia/Cppia.h, line 116 - I added afKeyValueIterator to the array functions right after the existing afIterator. Is there an external dependency on the exact order of these values?
• src/cppia/ArrayBuiltin.cpp, line 1697 - is the conversion to destType there just "convert to object"?
• include/Array.h and src/Array.cpp - I added a hx::ArrayKeyValueIterator class to mirror the hx::ArrayIterator one. I could not define the Dynamic next() method in the header file because I cannot include Anon.h in Array.h (cyclic dependency). The implementation of is in src/Array.cpp.

The CI failure seems to be related to the last point. I guess src/Array.cpp (or its object file) is not being linked wherever things from src/Array.h are used?

[hughsando]

The clsId is for "Std.is" - since you can't ask this for iterators (?), it does not matter.

The order of the ArrayFunc enum needs to match the gArrayFuncNames and gArrayArgCount order, but these are not saved to disk anywhere so just need to be consistent for the single compile.

It is quite possible the destType will be String (eg, "trace"). With some Dynamic stuff, it might end up being Int too, but the result would not be important here, since it's undefined behaviour.

I can't see the error, but I think it's because the c++ code needs to be able to "see" the definition if its templated. The best place to put this is in "include/hx/Operators.h" which comes after everything else is included.

[hughsando]

but also, good work.

[nadako]

@Aurel300 let's do this for 4.1 :)