Support custom slot suppliers #90
Description
The SlotSupplier type currently supports .fixedSize and .resourceBased variants. The bridge FFI layer also supports a Custom one with callback-based slot suppliers (TemporalCoreCustomSlotSupplierCallbacks), allowing users to implement their own slot allocation logic.
A custom slot supplier requires implementing these callbacks via a Swift protocol:
- reserveSlot — async reservation of a slot (called when a task needs a slot)
- tryReserveSlot — non-blocking attempt to reserve a slot
- markSlotUsed — called after a reserved slot begins processing a task
- releaseSlot — called when a task completes and its slot is freed
- availableSlots — returns the current number of available slots