Tries to emit a value to this shared flow without suspending. It returns
true if the value was emitted successfully (see below). When this function returns
false, it means that a call to a plain emit function would suspend until there is buffer space available.
If there are no subscribers, the buffer is not used. Instead, the most recently emitted value is simply stored into the replay cache if one was configured, displacing the older elements there, or dropped if no replay cache was configured. In any case,
This method is thread-safe and can be safely invoked from concurrent coroutines without external synchronization.