Merge branch 'ps/setup-centralize-odb-creation'

Merge branch 'ps/setup-centralize-odb-creation'

The setup logic to discover and configure repositories has been
refactored, and the initialization of the object database has been
centralized.

* ps/setup-centralize-odb-creation:
  setup: construct object database in `apply_repository_format()`
  repository: stop reading loose object map twice on repo init
  setup: stop initializing object database without repository
  setup: stop creating the object database in `setup_git_env()`
  repository: stop initializing the object database in `repo_set_gitdir()`
  setup: deduplicate logic to apply repository format
  setup: drop `setup_git_env()`
  t0001: plug test gaps for git-init(1) with GIT_OBJECT_DIRECTORY