Tune down DB upgrade dialogs

There would be more than one upgrade dialog per database at project
loading if the dialogs were cancelled. The dialogs would pop up
also when closing a project. This happens no more since DB manager
now keeps tabs on which database has shown the dialog. We ask
for upgrade again only when user tries to open an outdated database
in DB editor.

Re #2915

spinetoolbox/project_item/logging_connection.py

@@ -171,7 +171,7 @@ def has_filters(self):
             url = resource.url
             if not url:
                 continue
-            db_map = self._get_db_map(url, ignore_version_error=True)
+            db_map = self._get_db_map(url)
             if db_map is None:
                 continue
             known_filters = self._filter_settings.known_filters.get(resource.label, {})
@@ -184,9 +184,9 @@ def has_filters(self):
                     return True
         return False
 
-    def _get_db_map(self, url, ignore_version_error=False):
+    def _get_db_map(self, url):
         if url not in self._db_maps:
-            db_map = self._toolbox.db_mngr.get_db_map(url, self._toolbox, ignore_version_error=ignore_version_error)
+            db_map = self._toolbox.db_mngr.get_db_map(url, self._toolbox)
             if db_map is None:
                 return None
             self._db_maps[url] = db_map

spinetoolbox/spine_db_editor/widgets/spine_db_editor.py

@@ -162,7 +162,9 @@ def load_db_urls(self, db_url_codenames, create=False, update_history=True, wind
         self._changelog.clear()
         self._purge_change_notifiers()
         for url, codename in db_url_codenames.items():
-            db_map = self.db_mngr.get_db_map(url, self, codename=codename, create=create, window=window)
+            db_map = self.db_mngr.get_db_map(
+                url, self, codename=codename, create=create, window=window, force_upgrade_prompt=True
+            )
             if db_map is not None:
                 self.db_maps.append(db_map)
         if not self.db_maps:

spinetoolbox/spine_db_manager.py

@@ -120,6 +120,7 @@ def __init__(self, settings, parent, synchronous=False):
         self._validated_values = {"parameter_definition": {}, "parameter_value": {}}
         self._parameter_type_validator = ParameterTypeValidator(self)
         self._parameter_type_validator.validated.connect(self._parameter_value_validated)
+        self._no_prompt_urls = set()
 
     def _connect_signals(self):
         self.error_msg.connect(self.receive_error_msg)
@@ -316,6 +317,7 @@ def close_session(self, url):
         Args:
             url (str)
         """
+        self._no_prompt_urls.discard(url)
         db_map = self._db_maps.pop(url, None)
         if db_map is None:
             return
@@ -334,17 +336,17 @@ def close_all_sessions(self):
         for url in list(self._db_maps):
             self.close_session(url)
 
-    def get_db_map(self, url, logger, ignore_version_error=False, window=False, codename=None, create=False):
+    def get_db_map(self, url, logger, window=False, codename=None, create=False, force_upgrade_prompt=False):
         """Returns a DatabaseMapping instance from url if possible, None otherwise.
         If needed, asks the user to upgrade to the latest db version.
 
         Args:
             url (str, URL)
             logger (LoggerInterface)
-            ignore_version_error (bool, optional)
-            window (bool, optional)
-            codename (str, NoneType, optional)
-            create (bool, optional)
+            window (bool)
+            codename (str, optional)
+            create (bool)
+            force_upgrade_prompt (bool)
 
         Returns:
             DatabaseMapping, NoneType
@@ -361,8 +363,9 @@ def get_db_map(self, url, logger, ignore_version_error=False, window=False, code
             logger.msg_error.emit(err.msg)
             return None
         if prompt_data is not None:
-            if ignore_version_error:
+            if not force_upgrade_prompt and url in self._no_prompt_urls:
                 return None
+            self._no_prompt_urls.add(url)
             title, text, option_to_kwargs, notes, preferred = prompt_data
             kwargs = OptionsDialog.get_answer(
                 self.parent(), title, text, option_to_kwargs, notes=notes, preferred=preferred