Unify the behavior around backspacing iOS lists and quotes

[szydlovsky]

Previous PRs brought a bit of mayhem to lists and quotes on iOS in terms of their behavior consistency;

• the added utils that removed styles when all characters of a line were removed messed with the fact that lists and quotes shouldn't do that. A zero width space should appear there. Added a check in these utils for these styles.
• after fixing the above, zero width spaces still didn't appear in the first line because empty input "reset attributes" check was running first. Changed their order.
• cleaned up and fixed the logic for handling backspaces within lists. Now backspace that is visibly done on the list/quote marker only removes style, keeping the whole line intact
• also fixed one edge case to the above behavior, which resulted in the style being removed because the attributes magically weren't preserved