Streamline pagination tests

[wilsonianb]

Only populate the set of models (via createModel) once during pagination tests (instead of once for each test):

https://github.com/interledger/rafiki/blob/main/packages/backend/src/shared/baseModel.test.ts https://github.com/interledger/rafiki/blob/main/packages/backend/src/graphql/resolvers/page.test.ts

This requires changing table management in all test files using these pagination tests OR the pagination tests could be consolidated into a single test so that an outer beforeEach/afterEach can still truncate the corresponding table(s).

[sabineschaller]

@wilsonianb is the concern here just speed?

[wilsonianb]

@wilsonianb is the concern here just speed?

yeah