Remove duplicate enum declarations

[kxyr]

Identical enums that are defined in multiple files can be removed and reused instead. An example is the ExportResult enum used in the exporter.h file in the trace SDK and the logs SDK folders. Both implement the enum values kSuccess and kFailure. This enum could be shared instead of redefined in both places.

[anshulkumar19]

@xukaren I would like to work on this issue, can you please assign it to me. This seems a tech debt issue and can arise again if further code changes are not merged carefully keeping this in mind.
Do we have any process or guideline to avoid these kind of issues once fixed, maybe we can integrate a static analysis tool to detect code smells in PR itself.

[kxyr]

Yup, thanks so much. @open-telemetry/cpp-approvers should be able to assign you to this :)

[reyang]

@anshulkumar19 assigned to you, thanks!