We often call str.format() on translated strings.
E.g. `_("time left: {} seconds").format(t1)`
If the translated string has a different format syntax, this can raise at runtime.
This PR adds some runtime checks that try to ensure the source string and the translated string
have a similar format syntax. If the checks fail, `_()` will "reject" the translation by
returning the source string.
fixes https://github.com/spesmilo/electrum/issues/10010
ref https://github.com/spesmilo/electrum/issues/10007#issue-3203378250
d16c625019