Set up profiling, identify bottle necks

[mlange-42]

Modo🧯's processing times are ok, but not super duper fast. E.g. on an older laptop, the Mojo🔥 stdlib takes aroung 1.5
seconds to process. Average-sized packackes can be expected to take a few to a few dozens of milliseconds.

There are a lot of slice allocations in the code, and probably also a lot of string copying. A projiling project should be set up to identify where he most time is spent.

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A simple profiling setup can be found under test/profile

Insights

• Profiling on the Mojo stdlib shows that around 60% of time is spent writing out files
• Reduced run time by avoiding repeated RegExp compilation in Avoid repeated RegExp compilation #89