feat(logging): allow configuring the mock function used

[eventualbuddha]

Overview

Refs #5725

Unblocks converting packages that use @votingworks/logging's mock factories.

Demo Video or Screenshot

// jest by default
const logger = mockLogger();

// vitest by request
const logger = mockLogger({ fn: vi.fn });

Testing Plan

Converted libs/db, which uses mockBaseLogger, to use vi.fn.