Deprecate exclusivePrefixSum, accumulate, adjacentDifference, iota and provide KokkosExt ones

[aprokop]

ArborX::exclusivePrefixSum -> ArborX::Details::KokkosExt::exclusive_scan
ArborX::accumulate -> ArborX::Details::KokkosExt::reduce
ArborX::adjacentDifference -> ArborX::Details::KokkosExt::adjacent_difference
ArborX::iota -> ArborX::Details::KokkosExt::iota

Things I'm not sure about:

• Should be do KokkosExt::StdAlgorithms namespace?
• Should iota be in StdAlgorithms?

The goal of this and #998 is that ArborX_DetailsUtils.hpp is pretty clean post removal of deprecations, and nothing in ArborX:: namespace.

[dalg24]

Why did you not introduce the initial value trailing argument with exclusive_scan if the intent is to align with standard parallel algorithms?

[aprokop]

Why did you not introduce the initial value trailing argument with exclusive_scan if the intent is to align with standard parallel algorithms?

Right now, the only thing I've done is moving things around. I haven't done the alignment with the standard algorithms in this PR.
Added initial value.

[masterleinad]

Things I'm not sure about:

• Should be do KokkosExt::StdAlgorithms namespace?
• Should iota be in StdAlgorithms?

I don't think either of these are necessary (but it's easy to change since we don't care about backward-compatibility in that namespace).

[dalg24]

add a using-declaration and do unqualified call here and below

  using ArborX::Details::KokkosExt::reduce;

[aprokop]

I prefer the way I did it.

[dalg24]

Prefet

Suggested change

	namespace KokkosExt = ArborX::Details::KokkosExt;
	using ArborX::Details::KokkosExt::exclusive_scan;

[dalg24]

I would really like you to switch to using declaration in the unit test but I am not blocking