Provide APIs to retrieve scope data for Hybrid SDKs

[markushi]

Problem Statement

Main discussion is happening here: getsentry/team-mobile#11

Similar to cocoa we want to provide APIs to sync the current scope down to our Hybrid SDKs. As this only needs to be done on-demand, a pull-based approach should be sufficient.

Solution Brainstorm

~ ScopeUtil.serialize(scope: Scope)