Refactor polkadot-api mocks into a library

[shannonwells]

We have a lot of duplicated mocks of the polkadot-api library. It should be refactored into a test utility library of its own.

Also the polkadot-api logging can be really annoying; move this code into test setup:

jest.mock('@polkadot/util/cjs/logger', () => ({
  logger: () => ({
    debug: jest.fn(),
    error: jest.fn(),
    log: jest.fn(),
    warn: jest.fn(),
    noop: jest.fn(),
  }),
  loggerFormat: jest.fn((v) => v),
}));