fix: use logging macros instead of emitting event directly, so that it is also logged by tracing (#7459)

The events are needed when you are not using chatmail core from rust, if
you use chatmail core from your rust bot or from tauri, then you likely
already use the rust logging/tracing ecosystem. So it makes sense to use
it instead of listening to the events and logging them yourself.

This pr fixes a few cases where the event was direclty emitted instead
of using the macro and thus was not also automatically logged via
tracing.

src/accounts.rs

@@ -377,6 +377,11 @@ impl Accounts {
                 "Starting background fetch for {n_accounts} accounts."
             )),
         });
+        ::tracing::event!(
+            ::tracing::Level::INFO,
+            account_id = 0,
+            "Starting background fetch for {n_accounts} accounts."
+        );
         let mut set = JoinSet::new();
         for account in accounts {
             set.spawn(async move {
@@ -392,6 +397,11 @@ impl Accounts {
                 "Finished background fetch for {n_accounts} accounts."
             )),
         });
+        ::tracing::event!(
+            ::tracing::Level::INFO,
+            account_id = 0,
+            "Finished background fetch for {n_accounts} accounts."
+        );
     }
 
     /// Auxiliary function for [Accounts::background_fetch].
@@ -429,6 +439,11 @@ impl Accounts {
                 id: 0,
                 typ: EventType::Warning("Background fetch timed out.".to_string()),
             });
+            ::tracing::event!(
+                ::tracing::Level::WARN,
+                account_id = 0,
+                "Background fetch timed out."
+            );
         }
         events.emit(Event {
             id: 0,