Merge runtime overrides with sync configuration

Problem/Motivation

Currently, there are specific settings that defined in options or in the context rather than, or on top of, what is configured in the synchronization configuration properties. Most of those, if not all, turned out to be better positioned in the synchronization configuration. We should try to keep as much as possible in the synchronization configuration, and provide a generic mechanism to override any properties at runtime.

We still need to take into account the current situation, at least up to branch 5.x, for maintaining backwards compatibility.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes