Add plural forms for needed strings in NVDA's code base (#15864)
Closes #12445
Follow-up of #15013.
Summary of the issue:
When possible NVDA needs to distinguish between singular and plural in UI messages. The impact may be more significant in languages such as Slavic ones, where there are more than one plural form.
Description of user facing changes
In NVDA UI messages, i.e. in GUI or when NVDA speaks or brailles messages, messages will use singular/plural form as needed.
Description of development approach
Look for all strings containing "%" or "{" in the .pot and check if a plural form is needed. And replace _ / pgettext by ngettext / npgettext where needed.
Some expression containing a number have been pluralized even if they do not differ between singular and plural form in English due to the difference being visible in translations due to a different grammar. E.g.: "{numFingers} finger {action}" in English to be translated to "{action} {numFingers} doigt" (singular) vs "{action} {numFingers} doigts" (plural) in French.
table-rowcount and table-columncount control fields of the virtual buffer's text info have had to be converted to integer (previously strings), so that computation can be done.
No change log needed except for the code's API breaking change.
Testing strategy:
Manual smoke test on a subset of strings.
Feedback from translators during translation period and communication with the translators mailing list
