Update version to 2.50.0-pre1 (on v2.50.x branch)

[jtattermusch]

I'll release the -pre1 release after merging this.

[jtattermusch]

@JamesNK saw this test flake:

Passed!  - Failed:     0, Passed:   342, Skipped:    54, Total:   396, Duration: 1 m 24 s - Grpc.AspNetCore.FunctionalTests.dll (net6.0)
Test run for /home/runner/work/grpc-dotnet/grpc-dotnet/test/FunctionalTests/bin/Release/net7.0/Grpc.AspNetCore.FunctionalTests.dll (.NETCoreApp,Version=v7.0)
Microsoft (R) Test Execution Command Line Tool Version 17.4.0 (x64)
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
  Failed Refresh_Error_HasResult [5 s]
  Error Message:
   System.TimeoutException : The operation at /home/runner/work/grpc-dotnet/grpc-dotnet/test/FunctionalTests/Balancer/DnsResolverTests.cs:98 timed out after reaching the limit of 5000ms.
  Stack Trace:
     at Grpc.Tests.Shared.TaskExtensions.TimeoutAfter[T](Task`1 task, TimeSpan timeout, String filePath, Int32 lineNumber) in /home/runner/work/grpc-dotnet/grpc-dotnet/test/Shared/TaskExtensions.cs:line 72
   at Grpc.AspNetCore.FunctionalTests.Balancer.DnsResolverTests.Refresh_Error_HasResult() in /home/runner/work/grpc-dotnet/grpc-dotnet/test/FunctionalTests/Balancer/DnsResolverTests.cs:line 98
   at NUnit.Framework.Internal.TaskAwaitAdapter.GenericAdapter`1.BlockUntilCompleted()
   at NUnit.Framework.Internal.MessagePumpStrategy.NoMessagePumpStrategy.WaitForCompletion(AwaitAdapter awaiter)
   at NUnit.Framework.Internal.AsyncToSyncAdapter.Await(Func`1 invoke)
   at NUnit.Framework.Internal.Commands.TestMethodCommand.RunTestMethod(TestExecutionContext context)
   at NUnit.Framework.Internal.Commands.TestMethodCommand.Execute(TestExecutionContext context)
   at NUnit.Framework.Internal.Commands.BeforeAndAfterTestCommand.<>c__DisplayClass1_0.<Execute>b__0()
   at NUnit.Framework.Internal.Commands.BeforeAndAfterTestCommand.RunTestMethodInThreadAbortSafeZone(TestExecutionContext context, Action action)
  Standard Output Messages:
 0.000s GrpcTestContext - Information: Starting DnsResolverTests.Refresh_Error_HasResult
 0.001s Grpc.Net.Client.Balancer.PollingResolver - Trace: DnsResolver refresh requested.
 0.001s Grpc.Net.Client.Balancer.DnsResolver - Trace: Starting DNS query to get hosts from 'error.invalid'.
 5.007s GrpcTestContext - Information: Finishing DnsResolverTests.Refresh_Error_HasResult

Is that something we know of?

[JamesNK]

No

[jtattermusch]

No

I'm going to assume this is a test flake for now.