Explicitly type Image __init__ attributes

[Yay295]

No description provided.

[Yay295]

Unfortunately, trying to type im and palette leads to a lot of false errors because mypy can't always determine that those values aren't None.

Related:
python/mypy#10151
python/mypy#11969

[radarhere]

I've created #8279 as an alternative to this, addressing im and palette as well.

[Yay295]

Other than the im and palette changes, the only differences I see are a slightly different handling of PngImagePlugin, and a very different handling of EpsImagePlugin.

[radarhere]

I think my versions of the EPS and PNG changes are simpler. I've also restricted the hinting of self.info keys more than this PR.

[Yay295]

I'm not sure how you think your PNG change are simpler when you introduce a new local variable and I don't.

[radarhere]

My opinion is that it's simpler because my version declares what the type is once, whereas this does it three times.

[radarhere]

#8279 has been merged instead.