Use extended expression context for Control Panel actions

[erral]

This PR introduces a more flexible expression context for Control Panel actions.

By using get_current_context(), we can now use TALES expressions that depend on the current context (e.g., checking if a specific behavior is enabled on the current folder or document) when deciding whether to show a configlet in the control panel.

Changes:

• Added get_current_context() to Products.CMFPlone.utils to reliably find the current content object from the request.
• Updated PloneControlPanel.enumConfiglets to use the current context for expression evaluation.
• Added comprehensive tests for get_current_context().
• Removed an unused import in PloneControlPanel.py.

Fixes #3288

[mister-roboto]

@erral thanks for creating this Pull Request and helping to improve Plone!

TL;DR: Finish pushing changes, pass all other checks, then paste a comment:

@jenkins-plone-org please run jobs

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass, but it takes 30-60 min. Other CI checks are usually much faster and the Plone Jenkins resources are limited, so when done pushing changes and all other checks pass either start all Jenkins PR jobs yourself, or simply add the comment above in this PR to start all the jobs automatically.

Happy hacking!

[erral]

@jenkins-plone-org please run jobs

[gforcada]

LGTM without being an expert on this area of the code 😄

[erral]

@jenkins-plone-org please run jobs

[davisagli]

When is the control panel context NOT the portal? I'm not sure we should try to support that, since most control panels are global.

[erral]

When using addons like collective.lineage and lineage.controlpanels one can have control panels rendered in a child site or subsite (navigation roots).

To ease the managing of such scenarios, lineage.controlpanels modifies the controlpanels' url_expr to point it to ${plone_portal_state/navigation_root_url} but to be able to use plone_portal_state in such expressions, we need to enable extended expressions here.

See an example: https://github.com/collective/lineage.controlpanels/pull/13/changes#diff-a8395fbc089e4b85d51d34d18e6f6908a8fa864e291f81647f9bd542e3ad0746R23