.Net: Example of retry logic using Filters

[dmytrostruk]

Motivation and Context

Based on: #6105

This example shows how to perform retry with filter and switch to another model as a fallback.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄