add `dc_has_unnoticed_chats()` and `dc_marknoticed_all_chats()`

[Simon-Laux]

to fix this "bug" in desktop: https://github.com/deltachat/deltachat-desktop/issues/3979

if these information are not easily available in the UI, we should consider adding dedicated core functions as dc_has_unnoticed_chats() and dc_marknoticed_all_chats() (due to multiple meanings, we avoid the the term "read" in the api, cmp)

~ https://github.com/deltachat/deltachat-desktop/issues/3979#issue-2377575347

mainly important to have them in the jsonrpc api because thats what desktop uses