[#12048] Data migration: ensure consistency when script is stopped and resumed

[yuanxi1]

Part of https://github.com/TEAMMATES/teammates/issues/12048

Outline of Solution

• Using the cursor saving mechanism from base sql script as checkpoints
  1. Cursor position is saved after successfully migrating a course entity
  2. Cursor position is loaded when first start up the script, and the course entity A it points to if is not marked as migrated, a casecadeDelete method will be called to delete all related entities in the sql database and migration will restart from A.

Edit: CascadeType.REMOVE is already present for most parts of the chain but not present for Course-FeedbackSession, Course-User. For easier implementation for deleteCourseCascade, added cascade = CascadeType.REMOVE annotation for the two relations in Course.java.