Bug 1977743 - Extract MessageInjection from FolderDisplayHelpers. r=freaktechnik This stops MessageInjection from initialising unless the test actually intends for it to happen. Some tests have been depending on the account it creates, so instead I defined the account in preferences. Differential Revision: https://phabricator.services.mozilla.com/D257640

+
−component {22117140-9c6e-11d3-aaf1-00805f8a4905} nsSidebar.js
+
−contract @mozilla.org/sidebar;1 {22117140-9c6e-11d3-aaf1-00805f8a4905}
+
−category JavaScript-global-property sidebar @mozilla.org/sidebar;1
+
−category JavaScript-global-property external @mozilla.org/sidebar;1