base: don't allow selecting draft currencies by default
The initial intention was to "disallow invalidated", without forcing users to validate everything, but it was probably a mistake, if users don't need to validate then validation workflow would be a bit meaningless.
This is made after an incident where a user mistakenly cloned a validated currency and the cloned currency was available everywhere in the system.
Change to not return draft currencies by default and also change so that all items are tuple, for consistency. That should have no impact and is a bit easier for the test.
Also adjust accounting_ui_test, we need to validate currencies for the tests and clear cache if we validated some (but we don't need to clear cache if we validate accounts, because account caches is more clever and does not need to clear all cache)