Refactor test classes

[j-stephan]

This PR refactors some of our test classes. It also silences the following wrong g++-11 warning uncovered by #2107:

/builds/hzdr/crp/alpaka/include/alpaka/test/KernelExecutionFixture.hpp:47:15: error: 'fixture' may be used uninitialized [-Werror=maybe-uninitialized]
   47 |             : m_devHost{getDevByIdx(m_platformHost, 0)}
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /builds/hzdr/crp/alpaka/include/alpaka/acc/Traits.hpp:15,
                 from /builds/hzdr/crp/alpaka/include/alpaka/acc/AccCpuOmp2Blocks.hpp:27,
                 from /builds/hzdr/crp/alpaka/include/alpaka/alpaka.hpp:13,
                 from /builds/hzdr/crp/alpaka/include/alpaka/test/KernelExecutionFixture.hpp:7,
                 from /builds/hzdr/crp/alpaka/test/unit/intrinsic/src/Popcount.cpp:6:
/builds/hzdr/crp/alpaka/include/alpaka/platform/Traits.hpp: In function 'void CATCH2_INTERNAL_TEMPLATE_TEST_0() [with TestType = alpaka::AccCpuSerial<std::integral_constant<long unsigned int, 1>, long unsigned int>]':
/builds/hzdr/crp/alpaka/include/alpaka/platform/Traits.hpp:62:25: note: by argument 1 of type 'const alpaka::PlatformCpu&' to 'alpaka::Dev<TPlatform> alpaka::getDevByIdx(const TPlatform&, const size_t&) [with TPlatform = alpaka::PlatformCpu]' declared here
   62 |     ALPAKA_FN_HOST auto getDevByIdx(TPlatform const& platform, std::size_t const& devIdx) -> Dev<TPlatform>
      |                         ^~~~~~~~~~~
/builds/hzdr/crp/alpaka/test/unit/intrinsic/src/Popcount.cpp:60:47: note: 'fixture' declared here
   60 |     alpaka::test::KernelExecutionFixture<Acc> fixture(alpaka::Vec<Dim, Idx>::ones());
      |                                               ^~~~~~~

[bernhardmgruber]

Suggested change

QueueTestFixture() = default;

At this point you can just follow the rule of zero :)

[bernhardmgruber]

Suggested change

TestContainer() = default;