Add new default data sets to Mathesar #4138
Description
We've made some new data sets for use cases on our new website. We'd like to add them to Mathesar and allow users to import them when they create a new database (like we have with books and movies now).
Related PR: mathesar-foundation/mathesar-data-playground#20
As part of this, we should also remove our movies data set, but leave the books one in.