Typing for CloudOoo tests.

Adds type hints for Cloudooo tests. Pyright passes in strict mode.

We made use of the function _get_fonts from PyPDF, which, although prefixed by an underscore, it is intended to be public (https://github.com/py-pdf/pypdf/issues/153).

Some of these changes were proposed as part of !1628 (merged) , but were postponed due to differences in opinion about typing, until a consensus is achieved.