RFC for zip_view implementation, for oneDPL C++20

rfcs/proposed/zip_view/README.md

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+# zip_view Support for the oneDPL Range APIs with C++20
+
+## Introduction
+`std::ranges::zip_view` is a powerful utility that enables developers to combine two or more ranges into a single view,
+where each element is represented as a tuple containing corresponding elements from each input range.
+
+## Motivations
+`std::ranges::zip_view` is a convenient way to combine multiple ranges into a single view, where each element of
+the resulting range is a tuple containing one element from each of the input ranges. This can be particularly
+useful for iterating over multiple collections in parallel. `std::ranges::zip_view` was introduced in C++23,
+but many developers are still using C++20 standard. So, oneDPL introduces `oneapi::dpl::ranges::zip_view`,
+with the same API and functionality as `std::ranges::zip_view`.
+
+### Key Requirements
+`oneapi::dpl::ranges::zip_view` should be:
+- compilable with C++20 version (minimum)
+- API-compliant with `std::ranges::zip_view`
+- random accessible view; the "underlying" views also should be random accessible
+- in case of a device usage: a device copyable view itself and the "underlying" views also should be device copyable
+
+`oneapi::dpl::ranges::zip_view::iterator` should be:
+- value-swappable (https://en.cppreference.com/w/cpp/named_req/ValueSwappable)
+- implicitly convertible to `oneapi::dpl::zip_iterator`
+- able to be used with the non-range algorithms
+
+### Implementation proposal
+- `oneapi::dpl::ranges::zip_view` is designed as a C++ class which represents a range adaptor (see C++ Range Library).
+This class encapsulates a tuple-like type to keep a combination of two or more ranges.
+- The implementation provides all necessary operators to satisfy 'random accessible view' requirement.
+- To ensure device copyability, `oneapi::dpl::__internal::tuple` is proposed as a tuple-like type for underlying elements.
+- To provide a value-swappable requirement `oneapi::dpl::__internal::tuple` is proposed as a dereferenced value for
+`oneapi::dpl::ranges::zip_view::iterator` due to `std::tuple` not satisfying the value-swappable requirement in C++20.
+- Usage of C++ concepts is desirable to write type requirements for types, methods and members of the class.
+- C++20 is minimum supported version for the class. It allows using modern C++ features such as concepts and others.
+
+### Test coverage
+
+- `oneapi::dpl::ranges::zip_view` is tested itself, base functionality.
+- should be tested with at least one oneDPL range based algorithm.
+- should be tested with at least one oneDPL iterator based algorithm.