Fully qualify BlockTestCore::execution to avoid confusion with std::execution

[traversaro]

Fix robotology/robotology-superbuild#1646 .

This is a good example on why it is important not too use to much statements such as using namespace std. In blocktest, BlockTestCore::execution is defined, while since C++17 in the STL std::execution is defined.

The problem is hidden until someone includes (even transitively, that I guess it is why at the moment we have this feature only on a specific macos image) the <algorithm> headers that defines std::execution, and then you get errors like:

2024-05-09T02:39:26.7202600Z [5/31] Building CXX object CMakeFiles/blocktestyarpplugins.dir/src/actionCanWrite.cpp.o
2024-05-09T02:39:26.8205630Z FAILED: CMakeFiles/blocktestyarpplugins.dir/src/actionCanWrite.cpp.o 
2024-05-09T02:39:26.9219240Z /Users/runner/miniconda3/envs/test/bin/x86_64-apple-darwin13.4.0-clang++ -DBOOST_ATOMIC_DYN_LINK -DBOOST_ATOMIC_NO_LIB -DBOOST_FILESYSTEM_DYN_LINK -DBOOST_FILESYSTEM_NO_LIB -DBOOST_SYSTEM_DYN_LINK -DBOOST_SYSTEM_NO_LIB -Dblocktestyarpplugins_EXPORTS -I/Users/runner/work/robotology-superbuild/robotology-superbuild/b/src/blocktest-yarp-plugins -I/Users/runner/work/robotology-superbuild/robotology-superbuild/src/blocktest-yarp-plugins/src -I/Users/runner/work/robotology-superbuild/robotology-superbuild/b/src/blocktest-yarp-plugins/thrift -isystem /Users/runner/work/robotology-superbuild/robotology-superbuild/b/install/include/blocktestcore -isystem /Users/runner/work/robotology-superbuild/robotology-superbuild/b/install/include -march=core2 -mtune=haswell -mssse3 -ftree-vectorize -fPIC -fstack-protector-strong -O2 -pipe -stdlib=libc++ -fvisibility-inlines-hidden -fmessage-length=0 -isystem /Users/runner/miniconda3/envs/test/include -Wall -Wextra -O3 -DNDEBUG -std=gnu++17 -isysroot /Applications/Xcode_14.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -fPIC -MD -MT CMakeFiles/blocktestyarpplugins.dir/src/actionCanWrite.cpp.o -MF CMakeFiles/blocktestyarpplugins.dir/src/actionCanWrite.cpp.o.d -o CMakeFiles/blocktestyarpplugins.dir/src/actionCanWrite.cpp.o -c /Users/runner/work/robotology-superbuild/robotology-superbuild/src/blocktest-yarp-plugins/src/actionCanWrite.cpp
2024-05-09T02:39:27.0209090Z /Users/runner/work/robotology-superbuild/robotology-superbuild/src/blocktest-yarp-plugins/src/actionCanWrite.cpp:40:1: error: reference to 'execution' is ambiguous
2024-05-09T02:39:27.1209330Z execution ActionCanWrite::execute(const TestRepetitions& testrepetition)
2024-05-09T02:39:27.2210170Z ^
2024-05-09T02:39:27.3212920Z /Users/runner/work/robotology-superbuild/robotology-superbuild/b/install/include/blocktestcore/type.h:65:12: note: candidate found by name lookup is 'BlockTestCore::execution'
2024-05-09T02:39:27.4212430Z enum class execution
2024-05-09T02:39:27.5213500Z            ^
2024-05-09T02:39:27.6216620Z /Users/runner/miniconda3/envs/test/bin/../include/c++/v1/__type_traits/is_execution_policy.h:39:11: note: candidate found by name lookup is 'std::execution'
2024-05-09T02:39:27.7216070Z namespace execution {
2024-05-09T02:39:27.8217460Z           ^
2024-05-09T02:39:27.9220900Z /Users/runner/work/robotology-superbuild/robotology-superbuild/src/blocktest-yarp-plugins/src/actionCanWrite.cpp:52:16: error: reference to 'execution' is ambiguous
2024-05-09T02:39:28.0220540Z         return execution::continueexecution;
2024-05-09T02:39:28.1221880Z                ^
2024-05-09T02:39:28.2224610Z /Users/runner/work/robotology-superbuild/robotology-superbuild/b/install/include/blocktestcore/type.h:65:12: note: candidate found by name lookup is 'BlockTestCore::execution'
2024-05-09T02:39:28.3224220Z enum class execution
2024-05-09T02:39:28.4225190Z            ^
2024-05-09T02:39:28.5227630Z /Users/runner/miniconda3/envs/test/bin/../include/c++/v1/__type_traits/is_execution_policy.h:39:11: note: candidate found by name lookup is 'std::execution'
2024-05-09T02:39:28.6226860Z namespace execution {
2024-05-09T02:39:28.7227830Z           ^
2024-05-09T02:39:28.8230120Z /Users/runner/work/robotology-superbuild/robotology-superbuild/src/blocktest-yarp-plugins/src/actionCanWrite.cpp:111:12: error: reference to 'execution' is ambiguous
2024-05-09T02:39:28.9230430Z     return execution::continueexecution;
2024-05-09T02:39:29.0231810Z            ^
2024-05-09T02:39:29.1236500Z /Users/runner/work/robotology-superbuild/robotology-superbuild/b/install/include/blocktestcore/type.h:65:12: note: candidate found by name lookup is 'BlockTestCore::execution'
2024-05-09T02:39:29.2239410Z enum class execution
2024-05-09T02:39:29.3240670Z            ^
2024-05-09T02:39:29.4243270Z /Users/runner/miniconda3/envs/test/bin/../include/c++/v1/__type_traits/is_execution_policy.h:39:11: note: candidate found by name lookup is 'std::execution'
2024-05-09T02:39:29.5242920Z namespace execution {
2024-05-09T02:39:29.6252030Z           ^
2024-05-09T02:39:29.7253920Z 3 errors generated.

A more complete cleanup would be to try to avoid using namespace std, but at first I got a simple fix to the CI happy again.

[Nicogene]

Merged, thanks!