benchmarks/hyperfine: import package

A command-line benchmarking tool.
Features:
-Statistical analysis across multiple runs.
-Support for arbitrary shell commands.
-Constant feedback about the benchmark progress and current estimates.
-Warmup runs can be executed before the actual benchmark.
-Cache-clearing commands can be set up before each timing run.
-Statistical outlier detection to detect interference from other programs and
caching effects.
-Export results to various formats: CSV, JSON, Markdown, AsciiDoc.
-Parameterized benchmarks (e.g. vary the number of threads).

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