Improve how project terminal tab titles

This redoes how the project terminal tabs are displayed, specifically their titles (but I also added an icon!) If there's only one displayed - which is typical for most Kate projects - then it's just called "Terminal". If there is more than one tab shown, then they are further disambiguated like before.

The capitalization of "Terminal (Build)" is fixed, and the project terminal is now called "Terminal (Project)" instead of "Terminal (.kateproject)".