.NET: Sanitize user input in log statements for durable agent samples

[kshyju]

Description

Sanitize user input in log statements for durable agent samples.

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 adds log sanitization to two durable agent Azure Functions samples to prevent log forging/injection attacks by stripping \r and \n from user-provided values before they are included in structured log statements.

Changes:

• Added SanitizeLogValue helper methods to Tools.cs (non-nullable) and FunctionTriggers.cs (nullable) to strip carriage return and newline characters from log parameters.
• Wrapped user-provided values (topic, instanceId, conversationId, cursor) with SanitizeLogValue() in all log statements across both files.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
dotnet/samples/.../06_LongRunningTools/Tools.cs	Sanitizes topic and instanceId in log calls; adds non-nullable SanitizeLogValue helper
dotnet/samples/.../08_ReliableStreaming/FunctionTriggers.cs	Sanitizes conversationId and cursor in log calls; adds nullable SanitizeLogValue helper