Added Truncator Benchmarks

[smithdc1]

Added benchmarks for ticket #30686

@carltongibson -- Can I add this to your list? Aim is then to try and use the benchmark label on django/django

[smithdc1]

May be a bit much to add this permanently to the benchmark suite 🤷

[carltongibson]

Super. Thanks @smithdc1 — I will take a look next week! 👍

[smithdc1]

Just a short note to say I expect these benchmarks to show my current patch is much much slower (20x?!) for short truncations.

I've got a fix which will make it faster (2x?), but it needs more work to refine it.

So while I'd like it considering if these are suitable benchmarks. I need a bit more time to refine my proposed patch.

Something like asv continuous main [my prs commit hash] should show the diff.