Move load balancing configuration into a dedicated class

What does this MR do?

This moves load balancing configuration settings, such as the replication lag settings, into a dedicated class. This allows us to scope load balancer settings to load balancer instances, instead of being forced to use global settings. This in turn will make it easier to always enable the load balancing code, and to eventually support load balancing of multiple databases.

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
  • Backstage-only change, so no trailers are needed
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.