Reserve index 0 in SlotMap, improve unsafe collections

- Reserve index 0 as always invalid in SlotMap, ConcurrentSlotMap, UnsafeSlotMap, and UnsafeSparseSet; update all index checks and slot operations accordingly
- Refactor SlotMap to use parallel arrays and BitArray for occupancy
- Double capacity on resize for all major unsafe collections
- Add debugger display support for unsafe collections
- Improve NuGet publishing workflow to skip existing versions
- Increment package versions (LowLevel: 1.3.1, main: 1.0.2)
- Add comprehensive unit tests for SlotMap and ConcurrentSlotMap
- Update main program and documentation for new slot map behavior

Misaki.HighPerformance.Jobs/JobScheduler.cs

@@ -9,6 +9,13 @@ namespace Misaki.HighPerformance.Jobs;
 public unsafe partial class JobScheduler
 {
     public static readonly TempJobAllocator* pTempAllocator;
+
+    /// <summary>
+    /// Gets the allocation handle for the temporary job allocator.
+    /// </summary>
+    /// <remarks>
+    /// You must dispose the allocation before the fourth time you call <see cref="TempJobAllocator.AdvanceFrame"/> after obtaining this handle.
+    /// </remarks>
     public static AllocationHandle TempAllocatorHandle => pTempAllocator->Handle;
 
     static JobScheduler()