Move Kokkos::Array tests to a more suitable place

[dalg24]

Motivation: new place is a better fit and upcoming changes to view of Kokkos arrays where the remaining tests in that file would be removed

The Kokkos::Array tests are move from runtime view_aggregate test to TestArray.cpp that currently had CTAD compile-only tests. I split the tests into "aggregate initialization" and "zero-sized array code that must compile" and refactored to get the assertions checked at compile time. I did not really want to refactor further and actually run code on the device. I think that is good enough, the tests are easier to find and fairly readable.

These tests were introduced in 2017 and placed here for lack of a better place.

[dalg24]

[ 12%] Building CXX object core/unit_test/CMakeFiles/Kokkos_CoreTestCompileOnly.dir/TestArray.cpp.o
/var/jenkins/workspace/Kokkos_PR-6905/core/unit_test/TestArray.cpp: In function 'constexpr bool {anonymous}::test_array_zero_sized()':
/var/jenkins/workspace/Kokkos_PR-6905/core/unit_test/TestArray.cpp:113:8: error: call to non-'constexpr' function 'T& Kokkos::Array<T, 0, Proxy>::operator[](const iType&) [with iType = int; T = float; Proxy = void; Kokkos::Array<T, 0, Proxy>::reference = float&]'
     a[i] = T();
        ^
/var/jenkins/workspace/Kokkos_PR-6905/core/unit_test/TestArray.cpp: At global scope:
/var/jenkins/workspace/Kokkos_PR-6905/core/unit_test/TestArray.cpp:118:36: error: non-constant condition for static assertion
 static_assert(test_array_zero_sized());
               ~~~~~~~~~~~~~~~~~~~~~^~
/var/jenkins/workspace/Kokkos_PR-6905/core/unit_test/TestArray.cpp:118:36: error: 'constexpr bool {anonymous}::test_array_zero_sized()' called in a constant expression
make[2]: *** [core/unit_test/CMakeFiles/Kokkos_CoreTestCompileOnly.dir/build.make:79: core/unit_test/CMakeFiles/Kokkos_CoreTestCompileOnly.dir/TestArray.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:2033: core/unit_test/CMakeFiles/Kokkos_CoreTestCompileOnly.dir/all] Error 2

in SYCL build. Same issue in the CUDA 11.0 build and GCC-8.4
Other builds builds (surprisingly) went through.

[dalg24]

Failures are unrelated (various machine issues)