Task: Move Service Provider `Manager` abstraction to controller-utils

Description

Service providers velero, flux and eso currently contain duplicated controller logic that has been copied and adapted over time. This is especially the case for a Manager abstraction that has been introduced with the initial implementation of sp-velero and then copied over to sp-eso and sp-flux. This duplication increases maintenance overhead, creates inconsistencies between implementations and makes bug fixes difficult to roll out uniformly.

Moving the manager implementation to controller-utils could provide reference implementations for both flux based and native service providers which includes commonly required functionality like orphaned resource cleanup, version selection, secret sync etc. The manager module could then also be used in the service provider template example code generation.

Goals

• Reduce copy-pasted service provider code
• Centralize bug fixes and improvements to reduce maintenance efforts
• Improve consistency across service providers
• Provide reusable "flux implementation" for e.g. aso

Non-Goals

• Rewriting all existing service providers immediately

Done Criteria

• The Manager is consumable as reusable piece of code from controller-utils
• The Manager provides a fully functional implementation for basic flux based service providers that just want to deploy a HelmChart + OCIRepository
• Either sp-flux or sp-eso use the manager from controller-utils
• The Service Provider development guide points out the usage of the manager for flux based service providers.
• Code has been reviewed by other team members
• New / changed code is documented
• Unit Tests created for new code or existing Unit Tests updated
• Integration Test Suite updated
• Enduser Documentation updated (if applicable)
• Successful demonstration in Review