Consumption of local keycloak development fixtures should be improved

[jakedoublev]

Background

As a reference implementation of running the OpenTDF Platform and an identity provider, we have some Keycloak fixtures in use throughout the platform, and the implementation can be improved.

We deprecated the hardcoded keycloak provisioning from a CLI command in #1380 and now we should deprecate the logic underneath to lower maintenance burden.

Acceptance Criteria

1. Remove the SetUpKeycloak function in favor of only the SetUpCustomKeycloak function
2. Move example keycloak_data.yaml file to the fixtures module (possibly embedded)
3. Move service KC file loading logic into the lib/fixtures module
4. Deprecate duplicate logic in SetUpKeycloak likely to get out of sync with keycloak_data.yaml in the SDK Oauth tests
5. Ensure lib/fixtures is released with the changes in 1/2 so that the SDK and service modules are not broken, then consume the breaking fixtures change in the SDK and release it independently, doing the same for service module once the file is available.