Fix mark used API response serialization

[kfaraz]

Bug

For some APIs, DataSourcesResource and OverlordDataSourcesResource are not able to
serialize out the JSON response.

Note that the API is handled correctly by the server, it just fails to send back an appropriate response.

This bug was introduced a while back in #17545
While most of the APIs already handled sending back a JSON response,
some APIs didn't.

2025-06-12T01:40:01,545 ERROR [qtp41470360-100] com.sun.jersey.spi.container.ContainerResponse - 
Mapped exception to response: 500 (Internal Server Error)
javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: 
A message body writer for Java class org.apache.druid.rpc.indexing.SegmentUpdateResponse, 
and Java type class org.apache.druid.rpc.indexing.SegmentUpdateResponse, 
and MIME media type application/octet-stream was not found.

Fix

• Update all APIs in DataSourcesResource and OverlordDataSourcesResource to handle
  sending back a JSON response by annotating with @Produces(MediaType.APPLICATION_JSON)

Release note

Fix a bug with the following mark used / mark unused APIs so that they can send back a JSON response successfully.
Currently, these APIs work correctly but error out while sending back a response.

Method	Path	Description
POST	/druid/indexer/v1/datasources/{dataSourceName}	Mark all non-overshadowed segments as used
POST	/druid/indexer/v1/datasources/{dataSourceName}/markUsed	Mark non-overshadowed segments in an interval as used
POST	/druid/indexer/v1/datasources/{dataSourceName}/segments/{segmentId}	Mark a single segment as used
DELETE	/druid/indexer/v1/datasources/{dataSourceName}/segments/{segmentId}	Mark a single segment as unused
POST	/druid/coordinator/v1/datasources/{dataSourceName}	Mark all non-overshadowed segments as used
POST	/druid/coordinator/v1/datasources/{dataSourceName}/markUsed	Mark non-overshadowed segments in an interval as used
POST	/druid/coordinator/v1/datasources/{dataSourceName}/segments/{segmentId}	Mark a single segment as used
DELETE	/druid/coordinator/v1/datasources/{dataSourceName}/segments/{segmentId}	Mark a single segment as unused

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This PR has:

• been self-reviewed.
  • using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[kfaraz]

Thanks for the prompt review, @adarshsanjeev !