fix: replace deprecated pkg_resources

[desaxce]

Motivation for features / changes

Fixes #7003
When I run tensorboard, I get the deprecation warning, which I don't want:

.venv/lib/python3.12/site-packages/tensorboard/default.py:30: U
serWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pk
g_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refr
ain from using this package or pin to Setuptools<81.
  import pkg_resources

Technical description of changes

I replaced all occurrences of pkg_resources by importlib or packaging.version.

Screenshots of UI changes (or N/A)

==> not applicable

Detailed steps to verify changes work correctly (as executed by you)

I haven't run a thing, I have to go through the dev setup.

Alternate designs / implementations considered (or N/A)

--> not applicable

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.