cue: add a regression test for a structural cycle bug fixed in evalv3

The added bit of CUE incorrectly gives a result on evalv2,
but evalv3 correctly gives a structural cycle error.

Note that a lot of positions get unfortunately shifted
as we are adding an import at the top of the file.

Closes #3310.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I8b4bd4b1dda3ca7dadae242fb5489ecc1d980ec0
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1200808
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Matthew Sackman <[email protected]>

Author: mvdan