Remove usage of SaaSType enum

[galvana]

NOTE - this ticket has been re-created as ethyca/fides#1196 in fides repo, because it will be implemented in unified fides.

Is your feature request related to a specific problem?

SaaS connectors are in constant development and having tests that rely on a hard-coded list of connectors or connector counts causes issues during new development. We have to maintain awareness of which tests to update when a new connector is added but ideally this shouldn't be the case.

Describe the solution you'd like

• Remove the SaaSType enum
• Update any tests that assert a specific SaaS connector count to rely on the count of SaaS connectors from the SaaS connector registry
• Update any tests that rely on specific connectors to be present to be independent of which connectors are available
  • For example: test_search_connection_types and test_get_connection_types in tests/ops/api/v1/endpoints/test_connection_template_endpoints.py

[Kelsey-Ethyca]

There are ui dependencies on this. We will need to find another way to handle this on the frontend.