Write unit tests for ExporterConfiguration and then replace GSON with Jackson

[pihme]

Description

• Increase unit tests for exporter configuration and concrete exporter configuration users (e.g. ElasticsearchExporter, Debug Exporter etc.)
• Identify data types used for existing exporters
• Refactor implementation of data binding mechanism to use Jackson instead of GSON
• Verify that the behavior did not change

Background

• ExporterConfiguration is one of the last places where we use GSON, whereas in many other places we use Jackson consistently
• It is used to bind settings from a configuration source to instances of a exporter configuration classe´
• Ideally we would only use Jackson consistently throughout the codebase
• Changing the implementation is a bit risky. The default output of GSON and Jackson are not identical (e.g. for classes like Duration, DataSize), so changing the implementation will likely change behavior

[npepinpe]

Done in #9854