Rework the retry policy to be compatible with Polly via HttpClientFactory

[petrsvihlik]

Motivation

In order to be in line with Microsoft's best practices:

• https://docs.microsoft.com/en-us/dotnet/architecture/microservices/implement-resilient-applications/use-httpclientfactory-to-implement-resilient-http-requests
• https://docs.microsoft.com/en-us/dotnet/architecture/microservices/implement-resilient-applications/implement-http-call-retries-exponential-backoff-polly

we'd like to make our retry policy support compatible with Polly.