Don't expose `Internal.run_with_activation_context`

Currently, Internal.run_with_activation_context is still available at runtime and can be (mis)used in user configuration. I can't imagine a valid use case for this function there and its use would most likely result in an inconsistent state anyways (newly created objects that aren't properly synced/started).

For most members of Internal, Internal.remove("MemberName") is done at some point. The same could also be done for run_with_activation_context. However, we should also check if exposing this function to the DSL is even needed in the first place, or if we could just load the early config that uses this function in an activation context by default.

Start by locating Internal.run_with_activation_context and the existing Internal.remove patterns. Then inspect how early configuration is loaded and whether it already runs in an activation context. Done means reaching a decision on whether to remove the exposed function or change early configuration loading, with the issue's runtime exposure concern addressed.