Add Text benchmarks

[satotake]

Overview

I am trying #2599. I am not sure what is the focuses here. So, as a starting point, I added basic benchmarks for Unison.Util.Text vs. Data.Text. If this issue does not target Data.Text, I will remove them. And I have not done Bytes or Rope yet.

• It is not so helpful to increase n here. It might be good to limit the patterns.
• Some operations of Text underlying Rope (size, at) are faster than Data.Text

Interesting/controversial decisions

I ignored parser-typechecker/benchmarks/runtime/Main.hs tentatively. It was not updated and I tried to fix the regression. But I gave it up when I found that we need to use CombIx in Let.

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This change is 

[aryairani]

@satotake We have #2631 to fix benchmarks/runtime/Main.hs, sorry about that.

[satotake]

@aryairani no worries, sorry for missing that.