Add documentation for different sampling strategies available to clients

[black-adder]

Add this documentation to: http://jaeger.readthedocs.io/en/latest/client_libraries/

[Dieterbe]

yes. I could not find any docs about the sampling strategies, and in particular the dynamically adjustable one, how to adjust the rate at runtime. thanks!

[yurishkuro]

Is this not addressed by https://www.jaegertracing.io/docs/1.8/sampling/ ?

[SaarthakMaini]

I think this issue can be closed as Jaeger Clients have been retired

[yurishkuro]

@SaarthakMaini actually, this one makes me think that it would be great to update the whole "client_libraries" page to describe features in OTEL SDKs. #606