wallet: Translate [default wallet] string in progress messages

Noticed while reviewing https://github.com/bitcoin/bitcoin/pull/31287#discussion_r1843809721 that the [default wallet] part of progress messages remains untranslated while the rest of the string is translated.

Fix this in all places where CWallet::ShowProgress (which has a cancel button) and Chain::showProgress (which doesn't have a cancel button) are called by making "default wallet" into a translated string.