Add API for bulk/paged object deletion

iceberg and hbase could benefit from being able to give a list of individual files to delete -files which may be scattered round the bucket for better read peformance.

Add some new optional interface for an object store which allows a caller to submit a list of paths to files to delete, where
the expectation is

• if a path is a file: delete
• if a path is a dir, outcome undefined
  For s3 that'd let us build these into DeleteRequest objects, and submit, without any probes first.