Support passing parameters to GMA SDK in integration scenarios with rendering API.

[YuriyVelichkoPI]

Motivation

Here is a description of the problem from the Slack message:

In the original API, there was the option to attach publisherProvidedID and customTargeting to the GAMRequest. Is there an equivalent to this in the rendering API for iOS?

The integration scenario: https://docs.prebid.org/prebid-mobile/modules/rendering/ios-sdk-integration-gam.html

Objectives

Need to design and implement a solution that allows configuring the GMARequest object in the given integration scenario.

The issue is relevant for both platforms iOS and Android