Merge branch 'jt/receive-pack-use-odb-transactions' into HEAD

Merge branch 'jt/receive-pack-use-odb-transactions' into HEAD

'git receive-pack' has been refactored to use ODB transaction
interfaces instead of directly managing 'tmp_objdir' for staging
incoming objects, bringing it closer to being ODB backend agnostic.

* jt/receive-pack-use-odb-transactions:
  builtin/receive-pack: stage incoming objects via ODB transactions
  builtin/receive-pack: drop redundant tmpdir env
  odb/transaction: introduce ODB transaction flags
  odb/transaction: add transaction env interface
  odb/transaction: propagate commit errors
  odb/transaction: propagate begin errors
  object-file: propagate files transaction errors
  object-file: drop check for inflight transactions
  object-file: embed transaction flush logic in commit function
  object-file: rename files transaction fsync function
  object-file: rename files transaction prepare function