Migrate HTTP resilience integration from deprecated `Microsoft.Extensions.Http.Polly`

[carlostasada]

Description

Microsoft.Extensions.Http.Polly is deprecated in favor of Microsoft.Extensions.Http.Resilience. Replace the deprecated integration while preserving the SDK’s existing retry and resilience behavior across supported target frameworks.

Scope

• Replace Microsoft.Extensions.Http.Polly with Microsoft.Extensions.Http.Resilience.
• Update HTTP client resilience configuration to the new APIs.
• Preserve existing retry timing, retry count, and handled failure conditions.
• Update unit tests and package lock files.
• Remove the deprecated package after all usages are migrated.
• Confirm compatibility with netstandard2.0, netstandard2.1, net462, and the current modern .NET target.
• Exclude Broker API functionality.

Acceptance criteria

• No project references Microsoft.Extensions.Http.Polly.
• Existing resilience behavior remains covered by tests.
• Restore, Debug tests, Release build, and package validation pass without warnings.
• Lock files are regenerated and committed.
• Public API compatibility remains unchanged, or intentional differences are documented.
• Documentation and examples referencing the old integration are updated.

References

• Microsoft.Extensions.Http.Polly deprecation notice
• Microsoft.Extensions.Http.Resilience