Cpu perf

[Narsil]

What does this PR do?

Superseeds #2582

Instead of dropping stdin all the time (which break debugger interatictivity which is the reason for the introduction of this stdin reading code, we instead protect the stdin reading with debug level logger, where which the performance drop shouldn't be too surprising (jsut the sheer amount of logging slows everything down)

Fixes # (issue)

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