enabled and mitigated performance-avoid-endl clang-tidy warnings

[firewave]

This will also help with reducing valueFlowBailoutIncompleteVar warnings in our code base.

[firewave]

There is most likely some explicit flushes to be added to have a good CLI experience. I have not looked into it yet.

[firewave]

It seems the missing flushes somehow expose a bug in the pipe communication in the ProcessExecutor:

reportOut - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_2.cpp ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_2.cpp ...
reportOut - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_4.cpp ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_2.cpp ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_4.cpp ...
reportOut - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_1.qml ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_2.cpp ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_4.cpp ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_1.qml ...
reportOut - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_3.qml ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_2.cpp ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_4.cpp ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_1.qml ...
handleRead - Checking /tmp/pytest-of-user/pytest-8/test_markup_j0/test_3.qml ...

[firewave]

I cannot reproduce it outside of the Python test so it must be related to subprocess.Popen().