[dice] Adapt dice service and tests to the new DiceArtifacts trait

The code needed to be adpated because the public fields the code
accessed previously now become private. We need to access them
via the trait now.

This cl also deletes unused dependence libdiced_open_dice_cbor in
the dice service and tests targets.

Bug: 267575445
Test: m android.hardware.security.dice-service.non-secure-software
Test: atest VtsAidlDiceTargetTest VtsAidlDiceDemoteTargetTest
Change-Id: I16e18226c0bce8a90ed764ba598e90e7c1c854ab