Only the uses of `isinstance` against `InputPeer*` types were
reviewed. Notably, `utils` is exempt on this because it needs
to deal with everything on a case-by-case basis.
Since the addition of `*FromMessage` peers, any manual `isinstance`
checks to determine the type were prone to breaking or being
forgotten to be updated, so a common `helpers._entity_type()`
method was made to share this logic.
Since the conversion to `Peer` would be too expensive, a simpler
check against the name is made, which should be fast and cheap.
These two occur when replying to an inline query with a photo and
InputBotInlineMessageMediaAuto empty message, and passing URLs to
PNGs that may not be accessible (i.e. 403 from pixiv).
