Add custom job scheduling and dependency combiners

- Introduce `CombinedDependenciesJob` for efficient dependency handling and memory management
- Add `ScheduleCustom<T>` for user-defined job execution/free logic
- Refactor `JobInfo` and `JobDataPool<T>` for safer resource management and custom function support
- Improve SPMD extension type constraint formatting
- Update SPMD project content path and increment assembly versions
- Add unit tests for combined dependencies and custom jobs
- Remove `[Timeout]` from tests to prevent spurious failures
- Add TODO for future `WideLane` optimizations
- Replace legacy .sln with .slnx for better solution structure

Misaki.HighPerformance.Jobs/IJob.cs

@@ -1,3 +1,5 @@
+using System.Runtime.InteropServices;
+
 namespace Misaki.HighPerformance.Jobs;
 
 /// <summary>
@@ -39,6 +41,20 @@ public interface IJobParallel
     void Execute(int startIndex, int endIndex, ref readonly JobExecutionContext ctx);
 }
 
+internal unsafe struct CombinedDependenciesJob : IJob
+{
+    public JobHandle* dependencies;
+    public int dependencyCount;
+
+    public readonly void Execute(ref readonly JobExecutionContext ctx)
+    {
+        var span = new Span<JobHandle>(dependencies, dependencyCount);
+        ctx.JobScheduler.WaitAll(span);
+
+        NativeMemory.Free(dependencies);
+    }
+}
+
 public static class IJobExtensions
 {
     public static void Run<T>(this T job, ref readonly JobExecutionContext ctx)