Custom Markers for Workflow History/Timeline

Is your feature request related to a problem? Please describe.
I'd like to have the possibility to include workflow specific information like decisions or pivotal events inside history and/or timeline. I tried to Signal the same workflow without actually doing anything with the signal, but that's not permitted as described inside this issue. Currently, as a workaround, we expose those information inside queries, but nothing indicates someone (trying to find an error) that there is a query that can be used and these information would likely be booleans in most cases and therefore the queries actually don't seem to be handy for this demand.

Describe the solution you'd like
A way to record custom MarkerRecorded Events that are opaque for the server would be a suitable solution.

Describe alternatives you've considered
As mentioned before: Signaling (and ignoring) the own workflow which doesn't work either

Additional context
Add any other context or screenshots about the feature request here.

Start by reviewing issue #399 and the linked Temporal issue #682 to understand the history and signaling constraints. Determine the scope across Temporal workflow history and timeline handling, then define how opaque custom MarkerRecorded events would be represented and exposed; done means the behavior is specified well enough for SDK and compatibility testing.