ProcessExecutor: avoid explicit usage of suppressions

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The hasToLog() call performs this check.

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I am not sure this should be changed after all. The way the suppressions are checked is really hard to follow. I think we need some refactoring of where this is done so there's a single point for this and not two or three (or possibly more) of them. Will require some hacking and several other PRs merged first I guess.

[firewave]

I took another look and the change looks correct to me. Explicit usage of the suppressions feels wrong and it is issued by the parent process and the hasToLog() is used for all errors which are being transferred to it.

Also the test coverage of the suppressions is much more improved so if the CI passes we can be confident it doesn't trigger some weird side effect (which should not be happening at all since the behavior is functionally the same).