Fix packaging imports in version comparison logic (#8347)

Fixes #8349

### Description



The current behaviour is that `pkging, has_ver =
optional_import("packaging.Version")` always returns `has_ver=False`
because the import always fails (the `Version` class is exposed by the
`packaging.version` submodule).

This issue previously didn't surface, because when the import fails, it
would just continue to use the fallback logic. However, there seem to be
more hidden and more severe implications, which ultimately led me to
discovering this particular bug: Function like `floor_divide()` in
`monai.transforms` that check the module version using this logic are
called many times in common ML dataloading workflows. The failed imports
somehow can lead to OOM errors and the main process being killed (see
#8348). Maybe when
`optional_import` fails to import a module, the lazy exceptions somehow
stack up in memory when this function is called many times in a short
time period?

### 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).
- [ ] New tests added to cover the changes.
- [ ] Integration tests passed locally by running `./runtests.sh -f -u
--net --coverage`.
- [ ] 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.

monai/utils/module.py

@@ -540,11 +540,11 @@ def version_leq(lhs: str, rhs: str) -> bool:
     """
 
     lhs, rhs = str(lhs), str(rhs)
-    pkging, has_ver = optional_import("packaging.Version")
+    pkging, has_ver = optional_import("packaging.version")
     if has_ver:
         try:
-            return cast(bool, pkging.version.Version(lhs) <= pkging.version.Version(rhs))
-        except pkging.version.InvalidVersion:
+            return cast(bool, pkging.Version(lhs) <= pkging.Version(rhs))
+        except pkging.InvalidVersion:
             return True
 
     lhs_, rhs_ = parse_version_strs(lhs, rhs)
@@ -567,12 +567,12 @@ def version_geq(lhs: str, rhs: str) -> bool:
 
     """
     lhs, rhs = str(lhs), str(rhs)
-    pkging, has_ver = optional_import("packaging.Version")
+    pkging, has_ver = optional_import("packaging.version")
 
     if has_ver:
         try:
-            return cast(bool, pkging.version.Version(lhs) >= pkging.version.Version(rhs))
-        except pkging.version.InvalidVersion:
+            return cast(bool, pkging.Version(lhs) >= pkging.Version(rhs))
+        except pkging.InvalidVersion:
             return True
 
     lhs_, rhs_ = parse_version_strs(lhs, rhs)