[don't merge] api changes for time-skipping propagation

[feiyang3cat]

What changed and why?

Propagation refers to how time-skipping config is carried over to all workflows started by the current workflow: retry, continue-as-new, child workflows, reset, etc.

1. Remove disable_propagation and max_target_time, as neither can be accurately defined when time-skipping propagates transitively across related workflows:

• max_target_time: as an absolute time point, it may already have passed by the time a retry or downstream workflow starts, making it ambiguous whether to disable or preserve time-skipping — neither is a clearly correct default
• disable_propagation: it is unclear which type of transitively triggered workflow this should apply to, and treating all cases uniformly is unreasonable; we defer exposing this flexibility until user demand and use cases are better understood

2. Add comments documenting the default propagation behavior for each feature (retry, continue-as-new, child workflow, reset)
3. Add comments to explain bound
4. Add propagated skipped duration to time skipping config so that new workflows can inherit the virtual time

[feiyang3cat]

can be removed
but buf-breaking step in Makefile:115-117 will stop doing so