Type all @property in openpyxl

[Avasam]

• Overlaps Merge openpyxl stubs from microsoft/python-type-stubs #9511 to reduce changes there.
• Closes openpyxl Worksheet columns is incorrectly typed #10744 & closes fix openpyxl worksheet columns to return tuple[Cell, ...] #10745 (superseeds it)
• Typed all @property in openpyxl. And some related functions used by said properties (may as well do it now instead of having to redo the type analysis later).
• Validated that no @property or @abstractproperty is missing from source.
• Excluded worksheet-related properties in Workbook class. Those come with their own set of issues and difficulties.
• Changed a bytes to ReadableBuffer (relates to Track review of bytes types #9006)

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[srittau]

I didn't compare this to the implementation, but this all looks reasonable to me.