Remove dataspace_id column from Fragment table

Remove dataspace_id column from Fragment table

- Remove dataspace_id column from fragment table and drop associated
  index, foreign key constraint and uniqueness constaint.
- Add uniqueness constraint using only fragment xpath and anchor_id.
- Add not-null constraint to anchor_id.
- Update code and test data to remove references to dataspace_id.
- Repopulate the dataspace_id in Liquibase rollback
  (verified with manual testing of update/rollback).

Issue-ID: CPS-1677
Signed-off-by: danielhanrahan <daniel.hanrahan@est.tech>
Change-Id: I467cccba25ac5d884ec790064ca58150281b7e1d