cue/testdata: add a benchmark test for https://cuelang.org/issue/3514

To "lock in" the performance improvements in evalv3=1.

Closes #3514.

Signed-off-by: Paul Jolly <paul@myitcv.io>
Change-Id: I443d565a0682e420bca3e1b4d52007ecf85cb99b
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1208822
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>