cue/testdata/benchmarks: add benchmark for sort

Issue #745

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I6ad8ed5f59c8709f276da8a46858ab4fb9423c2e
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/549086
Reviewed-by: Daniel Martí <[email protected]>
Reviewed-by: Roger Peppe <[email protected]>
Unity-Result: CUEcueckoo <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

Author: mpvl