[BUG] DiskWriterQueue captures synchronization context

[alexbereznikov]

Version
LiteDB v5.0.19, Windows 11, .NET 6

Describe the bug
DiskWriterQueue captures synchronization context/task scheduler due to omitting task scheduler parameter in Task.Factory.StartNew. This can cause hard to debug side effects when custom synchronization contexts are being used. For contexts that can become invalid, Post call caused by state machine inside DiskWriterQueue.ExecuteQueue can break application.

Code to Reproduce
Unfortunately, I can't reproduce this issue in a new project.

Expected behavior
DiskWriterQueue should not capture synchronization context for its own operations.

Screenshots/Stacktrace
Part of the stack trace that leads to this error:

   at Zero.Foundation.Threading.TaskQueueSynchronizationContext.Post(SendOrPostCallback d, Object state) in C:\s\apollo.desktop\src\Zero.Foundation\Threading\TaskQueueSynchronizationContext.cs:line 40
   at System.Threading.Tasks.SynchronizationContextAwaitTaskContinuation.PostAction(Object state)
   at System.Threading.Tasks.AwaitTaskContinuation.RunCallback(ContextCallback callback, Object state, Task& currentTask)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__128_1(Object state)
   at System.Threading.QueueUserWorkItemCallback.<>c.<.cctor>b__6_0(QueueUserWorkItemCallback quwi)
   at System.Threading.ExecutionContext.RunForThreadPoolUnsafe[TState](ExecutionContext executionContext, Action`1 callback, TState& state)
   at System.Threading.QueueUserWorkItemCallback.Execute()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()
   at System.Threading.Thread.StartCallback()


Logs from custom synchronization context that shows what is being called:

POST <.cctor>b__8_0 System.Threading.Tasks.SynchronizationContextAwaitTaskContinuation+<>c
MoveNext System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1+AsyncStateMachineBox`1[System.Threading.Tasks.VoidTaskResult,LiteDB.Engine.DiskWriterQueue+<ExecuteQueue>d__14] System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1+AsyncStateMachineBox`1[System.Threading.Tasks.VoidTaskResult,LiteDB.Engine.DiskWriterQueue+<ExecuteQueue>d__14]


Additional context
In our case, integration tests started to fail after upgrading from v5.0.17 to v5.0.19. We're using a custom synchronization context to combine async code and transactions that are per-thread.

Introduced in f21cd84