Move all tests into an anonymous namespace

[elBoberido]

Brief feature description

All tests should be self contained in an anonymous namespace.

Detailed information

Multiple tests files are linked together into one binary. If the tests are not put into an unique namespace, it is possible that multiple helper structs with the same name but different layout are in the same binary. With luck, the linker complains. With bad luck, the address sanitizer detects some weird errors after doing something totally unrelated. Like renaming test files in #561 which lead to a different ordering in the compilation process and made the address sanitizer complain about heap buffer overflow due to 4 tests having a DummyData struct and one of them had a different layout.

TODO:

• utils moduletests
• utils integrationtets
• posh moduletests
• posh integrationtets
• dds moduletests
• binding_c moduletests