Sets anonymousId on track via Adjust's addPartnerParam method

[ladanazita]

Attribution data being sent back from Adjust is silently failing (since Segment requires one unique identifier (whether a userId or anonymousId on all calls), and the only way to send Adjust the Segment userId or anonymousId is through the setSessionPartnerParameter method, which we only mapped on identify. This now sets the anonymousId on all track events, so Segment can receive the Install Attributed event with the anonymousId attached.

We decided not to map userId because

1. analytics-ios does not have a getter function to retrieve the userId. We would have had to store to disc which take more time to implement, and this fix is urgent
2. Since the issue is around attribution events not having one of the required fields prior to identify being called, the anonymousId will be the only value present since identify has not been called and thus the userId has not been set

For Surfline, JIRA ticket here

[f2prateek]

LGTM