Improve qcolor-from-literal check and provide fixits
This takes into account the different patterns and provides a specific fixit or warning. Also, the #RRRGGGBBB color pattern which was previously ignored (10 characters long)
Example output from compiling Kirigami:
/home/user/kde/src/kirigami/src/platform/basictheme_p.h:149:52: warning: The QColor ctor taking RGB int value is cheaper than one taking string literals [-Wclazy-qcolor-from-literal]
QColor headerAlternateBackgroundColor = QColor{"#eff0f1"};
^~~~~~~~~
0xeff0f1
/home/user/kde/src/kirigami/src/platform/basictheme_p.h:150:38: warning: The QColor ctor taking RGB int value is cheaper than one taking string literals [-Wclazy-qcolor-from-literal]
QColor headerHoverColor = QColor{"#2196F3"};
^~~~~~~~~
0x2196F3
/home/user/kde/src/kirigami/src/platform/basictheme_p.h:151:38: warning: The QColor ctor taking RGB int value is cheaper than one taking string literals [-Wclazy-qcolor-from-literal]
QColor headerFocusColor = QColor{"#93cee9"};
^~~~~~~~~
0x93cee9