Port to AdwDialog and AdwAlertDialog

AdwDialog and AdwAlertDialog replaces AdwWindow and AdwMessageDialog respectively, improving adaptiveness. Several core apps are already using them.

• As part of this, gs_shell_modal_dialog_present() can be removed: !2128 (merged)

Migration guide: https://gnome.pages.gitlab.gnome.org/libadwaita/doc/main/migrating-to-adaptive-dialogs.html

AdwWindow → AdwDialog

• AdwAboutWindow: !1957 (merged)
• GsReposDialog: !1987 (merged)
• GsAppVersionHistoryDialog: !1980 (merged)
• GsReviewDialog: !1979 (merged)
• GsAppReviewsDialog: !1981 (merged)
• GsBasicAuthDialog: !1985 (merged)
• GsRemovalDialog: !1984 (merged)
• GsInfoWindow: !1982 (merged)
• GsUpdateDialog: !1988 (merged)
• gs_utils_show_error_dialog_simple: !2093 (merged)

AdwMessageDialog → AdwAlertDialog

• GsReposDialog > Enable Third-Party Software Repository?: !1987 (merged)
• GsReposDialog > Disable <repository>?: !1987 (merged)
• GsReposDialog > Enable <repository>?: !1987 (merged)
• Uninstall <app>?: !1989 (merged)
• Prepare <app>?: !1989 (merged)
• GsPage > gs_page_show_update_message (?): !1989 (merged)
• GsUpdatesPage> Charges May Apply: !2006 (merged)
• GsCommon> gs_app_notify_unavailable, gs_utils_show_error_dialog and gs_utils_ask_user_accepts: !2062 (merged)
• GsOverviewPage> Enable Third Party Software Repositories?: !2020 (merged)
• GsReviewRow> Report Review?: !2005 (merged)
• GsUpdatesPausedBanner> Software Updates Paused: !2021 (merged)

AdwWindow → AdwPreferencesDialog

• GsPrefsDialog: !1978 (merged)