C/C++ API doc: add some clearly visible page about error handling

[rouault]

Feature description

cf #13765 (review)

and perhaps generalities about the C/C++ GDAL API ?

Additional context

No response

[Sionigdha]

I see there was a recent PR merged referencing this issue — thanks for that.

There still seems to be room for a clearly visible, centralized page
documenting GDAL C/C++ error handling (error stack, return values,
usage patterns), which was the original intent of this issue.

I’d be happy to work on a documentation-only PR to address that,
if that sounds useful.