Snapshot tests: Sort attachments by name & TODO

* Avoid false positives on detecting changes due to changing in orders
  on attachments.
* TODO to remove cleaning up temporary files manually when cleanup
  improvements are merged.

application/apps/indexer/session/tests/snapshot_tests/snapshots/observe_dlt_session.snap

@@ -19,12 +19,12 @@ session_file:
   - "1970-01-01T00:00:00Z\u0004ecu\u00040\u0004\u00040\u0004\u0004ecu2\u0004\u0004\u0004LogLevel INFO\u0004\u0005FLFI\u00051005083951\u0005FLFI"
   - "1970-01-01T00:00:00Z\u0004ecu\u00040\u0004\u00040\u0004\u0004ecu3\u0004\u0004\u0004LogLevel INFO\u0004\u0005FLFI\u00052406339683\u0005FLFI"
 attachments:
+  - filename: test1.txt
+    content:
+      - test1
   - filename: test2.txt
     content:
       - test22
   - filename: test3.txt
     content:
       - test333
-  - filename: test1.txt
-    content:
-      - test1

application/apps/indexer/session/tests/snapshot_tests/utls.rs

@@ -66,6 +66,8 @@ impl SessionFiles {
             attachments.extend(atts_iter);
         }
 
+        attachments.sort_by(|att1, att2| att1.filename.cmp(&att2.filename));
+
         Self {
             session_file_lines,
             attachments,
@@ -74,6 +76,8 @@ impl SessionFiles {
 }
 
 /// Remove session main file and attachments for the given session file.
+/// TODO: This shouldn't be needed after the cleanup improvements are merged because the cleaning
+/// up will be called automatically when the session is dropped.
 pub fn cleanup_session_files(session_file: &PathBuf) {
     std::fs::remove_file(session_file)
         .expect("Removing generated temporary session file shouldn't fail");