[18.0][FIX] base_exception: enforce blocking check in wizard

[collinskipkorir]

Closes #3667

Problem

The confirmation wizard could allow blocking exceptions to be ignored when a downstream exception module set ignore_exception = True directly.

That write can remove the linked exceptions before action_ignore_exceptions() validates whether any exception is blocking.

Solution

Validate the wizard's original exception list before allowing exceptions to be ignored. The wizard then calls action_ignore_exceptions() to follow the standard ignore workflow.

Testing

• Added regression coverage for a downstream wizard that writes ignore_exception directly.
• The complete base_exception test suite passes.
• Pre-commit, Ruff, Ruff Format, and Pylint checks pass.
• Manually tested using purchase_exception.
• Confirmed that a blocking purchase exception raises an error and cannot be ignore

I confirm I have read the DCO (https://github.com/OCA/oca-addons-repo-template/blob/master/CONTRIBUTING.md) and signed it off.

@thomaspaulb help me review this

[OCA-git-bot]

Hi @sebastienbeau, @hparfr,
some modules you are maintaining are being modified, check this out!

[collinskipkorir]

I need a review to this

[collinskipkorir]

hi
@sebastienbeau i need a review on this