Script: switch to PEP 420 native namespace

[mauritsvanrees]

I have copied the script from zope meta and adapted it a bit for our packages.
I have added zest.releaser as dependency, because the script call bin/bumpversion.

I have applied it on plone.protect like this, first making the package for Plone 6.2 only:

• ./venv/bin/config-package --branch pep-420-native-namespace /Users/maurits/community/plone-coredev/6.2/src/plone.protect
• Edit .meta.toml and set:

• [tox]
  test_matrix = {"6.2" = ["*"]}
  

• ./venv/bin/config-package --branch pep-420-native-namespace --commit-msg "Set test matrix to 6.2 only." /Users/maurits/community/plone-coredev/6.2/src/plone.protect
• ./venv/bin/switch-to-pep420 --no-breaking /Users/maurits/community/plone-coredev/6.2/src/plone.protect

I have added --no-breaking, otherwise it wants to bump 6.0.0a2.dev0 to 7.0.0.dev0.

For most other packages we would not use this option, because we do want a major release. But then we first need to create an x.y maintenance branch, and change coredev 6.1 (and possibly 6.0) to use this branch in sources.cfg.

Resulting PR for plone.protect is here:
plone/plone.protect#138

[gforcada]

Looks great!

I made only a couple of minor observations :)

[gforcada]

On plone/documentation#1981 I mention this script, my idea would be that we merge this soonish, so we can create a new release of plone.meta and thus be able to uvx --from plone.meta switch-to-pep420 path/to/repository ✨