Feature Request: Rename oai_datacite and Datacite metadata exports

Overview of the Feature Request
So that Dataverse repository managers and others can more easily determine which exports to use, we'll rename the oai_datacite export to oai_openaire and the "Datacite" export to oai_datacite.

Before we can do this, the folks at OpenAIRE will need to change their systems and guidelines so that repository managers can tell OpenAIRE systems to harvest metadataPrefix named oai_openaire, instead of oai_datacite.

What kind of user is the feature intended for?
(Example users roles: API User, Curator, Depositor, Guest, Superuser, Sysadmin)
API User, Superuser, Sysadmin

What inspired the request?

• Reports of folks being confused about how the OpenAIRE/oai_datacite and DataCite/Datacite exports are named
• More recent shared understanding that we should continue to maintain the two exports, instead of merging them. See https://github.com/IQSS/dataverse/issues/11916#issuecomment-4048088747
• OpenAIRE folks seeming open to changing their systems and guidelines so that repository managers can tell OpenAIRE systems to harvest metadataPrefix named oai_openaire, instead of oai_datacite

What existing behavior do you want changed?
Changing the name of Dataverse's oai_datacite export to oai_openaire and changing the name of its "Datacite" export to oai_datacite.

Any open or closed issues related to this feature request?

• https://github.com/IQSS/dataverse/issues/5889
• https://github.com/IQSS/dataverse/issues/11916

No implementation files or tests are named. Start by locating the export definitions and metadataPrefix handling for oai_datacite and Datacite, then review issues 5889 and 11916 for context. Done means the distinct exports use oai_openaire and oai_datacite as requested, with related tests or documentation updated if present.