qt5: Add dark mode icon variants and detection
* qt5/icons/hint_dark.svg, qt5/icons/password-generate_dark.svg, qt5/icons/visibility_dark.svg: New. * qt5/icons/Makefile.am (EXTRA_DIST): Add icons. * qt5/pinentrydialog.cpp (PinEntryDialog::PinEntryDialog): Check if colorScheme is dark. Use Icons accordingly. * qt5/pinentrydialog.h (PinentryDialog): Add icon suffix member variable. * qt5/pinentryrc.qrc: Add new icons.
This is a backport of f4be34f83fd2079fa452525738ef19783c712438 for Qt 5.
Instead of using QGuiApplication::styleHints()::colorScheme() (which
didn't exist before Qt 6.5) we calculate the luminance of the button
color to check for dark mode.
- GnuPG-bug-id: T7737
