Reduce the flakyiess of simple_malloc

[r1viollet]

What does this PR do?

Change niceness level of the simple malloc process
This ensure that ddprof is scheduled with a higher priority.

Motivation

Less flaky tests.

[pr-commenter]

Benchmark results for collatz

Parameters

	Baseline	Candidate
config	baseline	candidate
profiler-version	ddprof 0.15.0+4701e9d7.21460863	ddprof 0.15.0+a1813c10.21464921

Summary

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1 metrics, 0 unstable metrics.

See unchanged results

scenario	Δ mean execution_time
scenario:ddprof -S bench-collatz --preset cpu_only collatz_runner.sh	same

[pr-commenter]

Benchmark results for BadBoggleSolver_run

Parameters

	Baseline	Candidate
config	baseline	candidate
profiler-version	ddprof 0.15.0+4701e9d7.21460863	ddprof 0.15.0+a1813c10.21464921

Summary

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1 metrics, 0 unstable metrics.

See unchanged results

scenario	Δ mean execution_time
scenario:ddprof -S bench-bad-boggle-solver BadBoggleSolver_run work 1000	unsure [+5.947ms; +12.645ms] or [+0.241%; +0.512%]