fix(runner): dont run health check in hot path

[not-matthias]

• Running the perf ping everytime before we receive a command puts unnecessary load on the other end, and also has the chance of failing to receive an answer in time.
• Also added a test to ensure the FIFO is cancel-safe. This can be an issue when we read the len but then timeout and drop the future, since read_exact isn't cancel-safe. So we'll never handle this command and the integration never receives a response
• Instead of using the perf fifo to check if the process is still alive, we now check if all the sub-processes terminates. The bash process will still exist since it will terminate on process.wait() after the FIFO handler terminates (an unfortunate limitation of having a single-threaded async runtime)

[codspeed-hq]

Merging this PR will not alter performance

✅ 4 untouched benchmarks

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_{Comparing cod-2057-perf-timeout-in-codspeed-go-makes-benchmark-hang (9035594) with main (06d99f2)}