Update UI item icons

[WilsonZiweiWang]

Sample results:

1. Moving Add an extra add-recipe operation with the plus icon to the title which can make adding recipes easier in case the list gets too long.
   2. Use less ambiguous icons for the build recipe and clean recipe operations

Icon references: https://code.visualstudio.com/api/references/icons-in-labels

[deribaucourt]

Elinor's feedback sounded like the new icons are not specially more meaningful. Also it would cause confusion to users of the previous version that now know them. I advise to keep those UI elements as they currently are. I like the additional button for adding a recipe to the list though. But we should also keep the previous one.

[ghost]

I think both icons are not the best for a build action, when I think of building I think more of a hammer for example.
But if Enguerrand's icon is also used for build actions in other extensions like CMake, I think it's a better idea.
Also the new icon for "clean" is not representative of the action for me.

[WilsonZiweiWang]

Okay, I will abandon the new icons but only keep the extra add icon in the title.