chore(deps): migrate to the official Zeebe Spring SDK

[chillleader]

Description

This PR will migrate the Connectors project to the official Camunda Spring SDK. Until now, we have been using the community-supported library Spring Zeebe which is now on a deprecation path.

Key changes:

• All Spring Boot apps are not using the new property structure for authentication-related config
• A community-supported Operate client is now used. The official Camunda Spring SDK doesn't offer an Operate client yet.
• All integration tests that had previously used the testing library from Spring Zeebe now use the official Camunda Process Test (CPT) library.
  • ⚠️ This will lead to significant increase in build time - each integration test case now takes 30+ seconds.
  • We can consider build optimizations due to this in a follow-up PR if this impacts our productivity
• Console Secret API client has been changed: it uses the authentication classes from the Operate client library. The check whether or not it should be enabled is done via the standard Zeebe client properties to cover the use cases where Operate is disabled and no properties are provided.
  • This is subject to change when Operate client becomes part of the Spring SDK.

Related issues

closes #2896