Signed-off-by: Wenqi Li <[email protected]>

### Description
this PR includes a few minor improvements
- allow string input, such as `device="cuda:1"` for Workflow
- skip stats key metric if `key_metric_name` is None
(monai/handlers/stats_handler.py)
- print incompatible metric values in the warning message
(CheckpointSaver)
- adds a `epochs` parameter for `ShuffleBuffer`
(Project-MONAI#5488)
- adds a `output_name_formatter` for `SaveImage`
(Project-MONAI#5508)
- simplify torch version in bundle init
(Project-MONAI#5529)

### Types of changes
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [x] Non-breaking change (fix or new feature that would not break
existing functionality).
- [ ] Breaking change (fix or new feature that would cause existing
functionality to change).
- [x] New tests added to cover the changes.
- [ ] Integration tests passed locally by running `./runtests.sh -f -u
--net --coverage`.
- [x] Quick tests passed locally by running `./runtests.sh --quick
--unittests --disttests`.
- [ ] In-line docstrings updated.
- [ ] Documentation updated, tested `make html` command in the `docs/`
folder.

Signed-off-by: Wenqi Li <[email protected]>
Signed-off-by: Nic Ma <[email protected]>
Co-authored-by: Nic Ma <[email protected]>
Signed-off-by: Behrooz <[email protected]>