New event for internal usage within package for logging errors; `UnifiedAnalyticsError`

[eliasyishak]

There are a few areas in the code for the analytics package where we may return null or silently reset the .dart-tool directory to ensure that the clients of this package don't crash the user using flutter, dart, or any other dash tool. We do this because having the analytics package fail should not block users from writing dart code, running flutter apps, etc.

However, there is still value for us to know what is happening to cause these issues. We should create a new event that is fired internally when these silent crashes happen so that we can be aware of what is happening. Or potentially look into setting up crash reporting as well.