This matches InfluxDB Cloud. The pagination was not exposed to the API,
but meant that API requests were limited to the default 20 pages.
Closes: #21407
* Move tenant.Service unit tests into its package
* Delete the top-level TenantService interface now that it's not used.
* Move helper funcs for setting up test stores into testing pkg
* Delete duplicate implementations scattered through the codebase
* Move error assertions into store-creation helpers
Sam Arnold
Daniel Moran
George MacRorie