openpyxl: Add _WorkbookChild / ReadOnlyWorksheet / Workbook annotations

[Avasam]

Extracted from #9511 and added all _WorkbookChild / ReadOnlyWorksheet / Workbook annotations I could find using the following search:

I updated parameter annotations for all of the following mathcing "whole word" regex:

• worksheet[,:\)]
• .*_worksheet[,:\)]
• sheets?[,:\)]
• ws[,:\)]
• parent[,:\)]
• wb[,:\)]
• workbook[,:\)]
• .*_workbook[,:\)]

And the return type of functions matching the following:

• def .*?workbook.*?\(
• def .*?sheet.*?\(

(note I looked for a few other variations of the above words, but they didn't match anything)

Now that typeshed has support for PEP 696, Workbook should probably be made generic on read_only and write_only, but that's out of scope for this PR. (see #9940 )

Added refs to python/mypy#6700

[github-actions]

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

[srittau]

Looks reasonable after spot checking.