This moves the internal iam service from the posix backend so
that we can start implementing new iam services right in the auth
module.
The internal iam service has same behavior as before, but now
must be enabled with the --iam-dir cli option.
New single user service is the default when no other iam service
is selected. This just runs the gateway in single user mode with
just the root account.
* feat: Added test an integration test case for acl actions(get, put), fixed PutBucketAcl actions bugs, fixed iam bugs on getting and creating user accounts
* fix: Fixed acl unit tests
* fix: Fixed cli path in exec command in acl integration test
* fix: fixed account creation bug
