SYSML21 — Deprecate Successions from "State::start" and "State::entryAction"

As part of the Users WG in coordination with Execution WG, we have determined that successions from the "start" of a state or the "entryAction" of the state can cause confusion for many users. As such, we want to "deprecate" this usage in favor of requiring an explicit state transition from "start" to the first subState.

We will need to update all of our relevant graphical and textual examples shown in the spec to demonstrate this preferred approach and remove the previous approach.

Models using successions from "start" or "entryAction" will remain valid but will not be the preferred method. We will want to indicate that support for such may be removed in some future version, subject to a discussion around what the deprecation policy should be.