Do ephemeral deletion in async task background loop (#3194)

* Do ephemeral deletion in background loop

1. in start_io start ephemeral async task, in stop_io cancel ephemeral async task

2. start ephemeral async task which loops like this:

- wait until next time a message deletion is needed or an interrupt occurs (see 3.)
- perform delete_expired_messages including sending MSGS_CHANGED events

3. on new messages (incoming or outgoing) with ephemeral timer:

- interrupt ephemeral async task

* Changelog

* Fix and improve test

* no return value needed

* address @link2xt review comments

* slight normalization: have only one place where we wait for interrupt_receiver

* simplify sql statement -- and don't exit the ephemeral_task if there is an sql problem but rather wait

* Remove now-unused `ephemeral_task` JoinHandle

The JoinHandle is now inside the Scheduler.

* fix clippy

* Revert accidental move of the line

* Add log

Co-authored-by: holger krekel <holger@merlinux.eu>
Co-authored-by: link2xt <link2xt@testrun.org>

src/chatlist.rs

@@ -9,7 +9,6 @@ use crate::constants::{
 };
 use crate::contact::{Contact, ContactId};
 use crate::context::Context;
-use crate::ephemeral::delete_expired_messages;
 use crate::message::{Message, MessageState, MsgId};
 use crate::stock_str;
 use crate::summary::Summary;
@@ -91,12 +90,6 @@ impl Chatlist {
         let flag_no_specials = 0 != listflags & DC_GCL_NO_SPECIALS;
         let flag_add_alldone_hint = 0 != listflags & DC_GCL_ADD_ALLDONE_HINT;
 
-        // Note that we do not emit DC_EVENT_MSGS_MODIFIED here even if some
-        // messages get deleted to avoid reloading the same chatlist.
-        if let Err(err) = delete_expired_messages(context).await {
-            warn!(context, "Failed to hide expired messages: {}", err);
-        }
-
         let mut add_archived_link_item = false;
 
         let process_row = |row: &rusqlite::Row| {