Dynamically adjusting configuration not intuitive since migrated to a struct

[Jeehut]

A user has recently reported that they would like to dynamically disable TelemetryDeck based on user configuration changes. But with the recent change of the configuration to being a struct, a new call to TelemetryDeck.initialize needs to be made to adjust the configuration, because it's no longer a reference type which can be changed from anywhere. While that has been a potential thread-unsafety issue, we should provide a simpler API to make these kinds of adjustments anywhere where dynamically changing the configuration options makes sense. For example, we could simply turn the analyticsDisabled bool into a sendable closure that returns a bool, similar to the new defaultParameters. This makes the setting dynamic while being thread-safe.