fix: Save msgs to key-contacts migration state and run migration periodically (#6956)

Save:
- (old contact id) -> (new contact id) mapping.
- The message id starting from which all messages are already migrated.
Run the migration from `housekeeping()` for at least 500 ms and for >= 1000 messages per run.

src/constants.rs

@@ -257,6 +257,9 @@ pub(crate) const ASM_BODY: &str = "This is the Autocrypt Setup Message \
     If you see this message in a chatmail client (Delta Chat, Arcane Chat, Delta Touch ...), \
     use \"Settings / Add Second Device\" instead.";
 
+/// Period between `sql::housekeeping()` runs.
+pub(crate) const HOUSEKEEPING_PERIOD: i64 = 24 * 60 * 60;
+
 #[cfg(test)]
 mod tests {
     use num_traits::FromPrimitive;