* SingleExecutor: added TODOs
* test `SingleExecutor` with files and project
* SingleExecutor: process markup files after code when scanning project
* TestSingleExecutor: generate scoped files before calling executor
* CI-unixish.yml: added `--output-on-failure` to CTest call
* helpers.cpp: improved error reporting in `~ScopedFile()`
* use unique filenames in executor tests to avoid collisions
* fixed `functionStatic` selfcheck warnings
* added asserts to make sure executors are only used in the intended context
* TestSuppressions: specify proper job counts in `checkSuppression*()`
* TestSuppressions: enabled all asserts in `runChecks()`
* TestSuppressions: removed unnecessary setting from `checkSuppression()`
* TestSuppressions: small cleanup in the way tests are called
* TestSuppressions: use `SingleExecutor`
* added `Settings::useSingleJob()` and use it instead of checking `jobs` or `jointSuppressionReport`
* extracted single job execution into `SingleExecutor`
* moved `reportStatus()` from `CppCheckExecutor` to Èxecutor
* TestSingleExecutor: improved tests
* added testing of markup extension handling in executors
* cleaned up includes based on `include-what-you-use`
* testsingleexecutor.cpp: suppress `performance-unnecessary-value-param` clang-tidy warnings
* ProcessExecutor: send color via pipe instead of applying it beforehand
* do not unconditionally apply colors to output / disable all colors in tests / adjusted tests for changed output behavior
* fixed precision loss in `Executor::reportStatus()`
* fixed `naming-varname` selfcheck warnings
Oliver Stöneberg