.NET: Align sample build configuration with test runner in CI

[kshyju]

Description

Match sample build configuration to test build configuration

Pass -c {BuildConfiguration} to dotnet run and dotnet build when launching sample projects during integration tests. BuildConfiguration is derived from the test project's own build config via #if DEBUG, ensuring samples
are built in the same configuration as the tests (Release in CI, Debug locally).

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This PR updates the Azure Functions integration tests to build and run the sample function apps in Release configuration, aligning test execution with production-like settings.

Changes:

• Run workflow sample function apps via dotnet run -c Release.
• Build durable agents sample projects via dotnet build -c Release.
• Run durable agents sample function apps via dotnet run --no-build -c Release.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
dotnet/tests/Microsoft.Agents.AI.Hosting.AzureFunctions.IntegrationTests/WorkflowSamplesValidation.cs	Runs workflow Azure Functions sample app in Release mode.
dotnet/tests/Microsoft.Agents.AI.Hosting.AzureFunctions.IntegrationTests/SamplesValidation.cs	Builds and runs durable agents Azure Functions sample app in Release mode.