Remove unused C convert method

[radarhere]

Part of #8389

[akx]

I was looking at this earlier too. Should we take the opportunity to also rename the functions/methods to something a little more descriptive?

[radarhere]

You'd like to rename convert2? Ok, to what? convert_to_image?

Or, if you want, we could suggest combining it with new_block, and go for a single, clear convert_to_block.

[akx]

You'd like to rename convert2?

It isn't a great name, is it? 😅

Ok, to what? convert_to_image?

convert_into would be closer, maybe, since AIUI it converts self into the format of the caller-allocated im?

Or, if you want, we could suggest combining it with new_block, and go for a single, clear convert_to_block.

I'd maybe skip that, because you could maybe want to use convert_into with a new_arrow allocated image too?

EDIT: I had to look up what new_block does: it allocates an image in a single contiguous block (because that's what Tk needs).

[radarhere]

I've created #9911