[OPT-7233] Create abstraction layer (ES) event Writers

Refactor these writers to Elasticsearch:

./backend/src/main/java/org/camunda/optimize/service/es/writer/CamundaActivityEventWriter.java

./backend/src/main/java/org/camunda/optimize/service/es/writer/EventProcessDefinitionWriter.java

./backend/src/main/java/org/camunda/optimize/service/es/writer/EventProcessInstanceWriter.java

./backend/src/main/java/org/camunda/optimize/service/es/writer/EventProcessMappingWriter.java

./backend/src/main/java/org/camunda/optimize/service/es/writer/EventProcessPublishStateWriter.java

./backend/src/main/java/org/camunda/optimize/service/es/writer/EventSequenceCountWriter.java

./backend/src/main/java/org/camunda/optimize/service/es/writer/EventTraceStateWriter.java

./backend/src/main/java/org/camunda/optimize/service/es/writer/ExternalEventWriter.java

Testing notes

These code changes should not cause any behaviour change in Optimize, as they are just code-refactoring. A normal regression testing is enough

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