mgr/prometheus: use vendored "packaging" instead

mgr/prometheus: use vendored "packaging" instead

* Note: The cherry-pick is altered, the original commit couldn't be cherry-picked
	as is since we introduced some changes in the organization of the debian dir
	(ceph-mgr-modules-core.requires doesn't exist yet).
	All the packages listed in main's ceph-mgr-modules-core.requires are marked
	as pkg.ceph.check in P/Q debian/control.
	Therefore, python3-pkg-resources is listed as <pkg.ceph.check> in debian/control.

instead of using the top-level "packaging" module, use the one
vendored by setuptools.

packaging python module provides versioning defined by PEP-440.
but python3-packaging is provided by CentOS8 powertools repo,
which is not enabled by default. and in CentOS9, this package
is provided by AppStream instead of BaseOS.

as prometheus mgr module is included by ceph-mgr-module-core,
it would be desirable if our user can install ceph-mgr-module-core
without enabling powertools or AppStream repo on a CentOS or
its derivative distros.

fortunately, setuptools vendors packaging module. and both
CentOS8 and CentOS9 provide python3-setuptools in their BaseOS
repos.

in this change, instead of using "packging" module, we use the
venderored one, which is in turn embedded in pkg_resources.
this python module is provided by python3-setuptools on CentOS
distros, and python3-pkg-resources on Debian and its derivatives

the packaging recipes are updated accordingly to reflect the
new runtime dependency.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>
(cherry picked from commit cf6089200d96fc56b08ee17a4e31f19823370dc8)

Signed-off-by: Matan Breizman <mbreizma@redhat.com>