Add AutoDilate metadata to TestKit timeout parameters

[Aaronontheweb]

Fixes #8440

Related to akkadotnet/akka.analyzers#148.

Summary

• add public parameter-level AutoDilateAttribute metadata to Akka.TestKit
• annotate caller-supplied durations that TestKit always scales, including EventFilter and cluster TestKit wrappers
• leave raw, interval, idle, epsilon, and conditionally dilated durations unannotated
• correct AwaitConditionNoThrow documentation to match its raw timeout behavior
• add reflection-based positive and negative metadata contract tests and update API approvals

The Akka.Remote.TestKit audit found no additional caller-supplied duration parameters that automatically apply the TestKit time factor.

Validation

• dotnet build src/core/Akka.TestKit/Akka.TestKit.csproj -c Release
• dotnet build src/core/Akka.Cluster.TestKit/Akka.Cluster.TestKit.csproj -c Release
• dotnet build src/core/Akka.Remote.TestKit/Akka.Remote.TestKit.csproj -c Release
• dotnet test src/core/Akka.TestKit.Tests/Akka.TestKit.Tests.csproj -c Release (324 passed, 1 skipped)
• dotnet test src/core/Akka.Remote.TestKit.Tests/Akka.Remote.TestKit.Tests.csproj -c Release (15 passed, 2 skipped)
• dotnet test src/core/Akka.Cluster.Tests.MultiNode/Akka.Cluster.Tests.MultiNode.csproj -c Release --filter FullyQualifiedName~AutoDilateMetadataSpec (2 passed)
• dotnet test src/core/Akka.API.Tests/Akka.API.Tests.csproj -c Release --filter FullyQualifiedName=Akka.API.Tests.CoreAPISpec.ApproveTestKit (1 passed)
• dotnet format verification for the three newly added C# files

[Aaronontheweb]

LGTM