qt,tests: Add helper to hook up the test passphrase provider
* lang/qt/tests/t-support.h, lang/qt/tests/t-support.cpp (class QGpgMETest): Add member function hookUpPassphraseProvider. Add member mPassphraseProvider. * lang/qt/tests/t-changeexpiryjob.cpp, lang/qt/tests/t-encrypt.cpp, lang/qt/tests/t-remarks.cpp, lang/qt/tests/t-tofuinfo.cpp, lang/qt/tests/t-trustsignatures.cpp, lang/qt/tests/t-various.cpp: Use new helper.
- GnuPG-bug-id: T5770