Configurable semantic colors

Add a page under _Color Themes -> Highlighting Text Styles -> KDevelop/Semantic Colors_ that allows the configuration of the semantic highlight colors.
- When the _Local colorization intensity_ is bigger than zero then the rainbow colors are used for local variables like before, overwriting the corresponding configured colors
- A _Global colorization intensity_ less then 255 (max) will still cause a blending of the global colors
- _Bold font for declarations_ will make the declarations bold in addition to the bold settings from the config dialog

So a _Local colorization intensity_ of 0 and a _Global colorization intensity_ of 255 should be set when the exact configured colors are desired.

See also:
https://invent.kde.org/kdevelop/kdevelop/uploads/500467bc355906d363e3a76a9044e138/ColorConfig.png

BUG: 395856