gui2/addon_manager: Re-read add-on versions after each update batch

The Update All codepath is unique in that it doesn't trigger a re-read
of add-on versions until the very end, once the full run has completed.
The problem with this is that install_addon_with_checks() may update
dependencies of individual add-ons in the process, resulting in
redundant downloads of any affected add-ons if the player isn't paying
attention.

Address this by triggering a re-read of add-on versions after every
single update batch that results in a download.

Closes #3273.

changelog.md

@@ -1,4 +1,7 @@
 ## Version 1.15.3+dev
+ ### Add-ons client
+   * Ensure the client doesn't re-download dependencies that have just been updated during an Update All
+     run by re-reading add-on versions after each update batch (issue #3273).
 
 ## Version 1.15.3
  ### AI

src/gui/dialogs/addon/manager.cpp

@@ -704,6 +704,13 @@ void addon_manager::update_all_addons(window& window)
 		if(tracking_info_[a.first].state == ADDON_INSTALLED_UPGRADABLE) {
 			addons_client::install_result result = client_.install_addon_with_checks(addons_, a.second);
 
+			if(result.wml_changed) {
+				// Updating an add-on may have resulted in its dependencies being updated
+				// as well, so we need to reread version info blocks afterwards to make sure
+				// we don't try to re-download newly updated add-ons.
+				refresh_addon_version_info_cache();
+			}
+
 			// Take note if any wml_changes occurred
 			need_wml_cache_refresh_ |= result.wml_changed;
 		}