[TECH DEBT]: Let `python_ast.MaybeTree` have multiple failures

[JCZuurmond]

Is there an existing issue for this?

• I have searched the existing issues

Problem statement

Let python_ast.MaybeTree have multiple failures as a notebook can have multiple parsing failures: one for each cell.

Proposed Solution

Refactor failure: str to failures: list[str], then rewrite NotebookLinter to return MaybeTree instead of tuple[Tree, list[Failures]]

Additional Context

No response

[JCZuurmond]

Not 100% sure if we should do this