What does this PR do?

Uses shutil.which in place of distutils.spawn.find_executable for Python 3 to remove dependency on distutils

Motivation

AI-2974. We want to get rid of distutils because its version in the stdlib is essentially deprecated, and the replacement used by setuptools increases the agent's memory footprint. This is the only place in core integrations that uses distutils directly.

Additional Notes

The reason that distutils is still used for Python 2 is that shutil.which was added on Python 3.3. There are less concerns about the use of distutils in Python 2, so missing a simple stand-in, it's fine to keep the statu quo there.

I haven't found a good way to add an integration test for this, so I've done a simple manual sanity check on the e2e environment to ensure this is doing what we expect:

root@docker-desktop:/# /opt/datadog-agent/embedded/bin/python
  Python 3.8.16 (default, Mar 27 2023, 11:47:24)
  [GCC 5.4.0 20160609] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  >>> from datadog_checks.network.network import find_executable
  >>> find_executable('ss')
  '/usr/bin/ss'

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached
• If the PR doesn't need to be tested during QA, please add a qa/skip-qa label.