Flaky tests

An issue to track flaky tests, and mark them with X X X like "upvotes".

* `tests/test_executable.py::test_executable[False-python-pyperf]` & `tests/test_executable.py::test_executable[True-python-pyperf]` due to ebpf helpers failure `b'stack not found, searched for 16384 bytes into task_struct\n'`. https://github.com/Granulate/gprofiler/runs/8218001478?check_suite_focus=true#step:7:414 https://github.com/Granulate/gprofiler/issues/523 X X X
* `test_from_container_spawned_process[False-java-ap]` - app seems to start too late and gProfiler misses it with async-profiler and we get perf samples. Then the app is leaked and subsequent tests fail due to 2 java apps running (and 1 is expected). We need to ensure the app is killed when the test is stopped, and/or remove the limitation of "1 app" and instead work with direct PIDs. https://github.com/Granulate/gprofiler/actions/runs/3059419376/jobs/4937080466 X X created #514
* `test_python_ebpf[False-python]` - PyPerf doesn't write the outputs upon being signaled. https://github.com/Granulate/gprofiler/actions/runs/3059444596/jobs/4937131682 X
* `ValueError: auxv id 31 was not found!` https://github.com/Granulate/gprofiler/actions/runs/3075034452/jobs/4968269992 for `test_executable_not_privileged[True-application_docker_capabilities0-python-py-spy-True]`. X X
* `tests/test_sanity.py::test_phpspy[False-php] - KeyError: XXX` (PID was not profiled) https://github.com/Granulate/gprofiler/actions/runs/3131599155/jobs/5083628149. X
* `test_from_container_spawned_process` flaky failure - app starts "too late" - #513
* Tests getting stuck forever - https://github.com/Granulate/gprofiler/issues/527
* nodejs attach-maps - https://github.com/Granulate/gprofiler/issues/538 X