Everywhere: Add sv suffix to strings relying on StringView(char const*)

Each of these strings would previously rely on StringView's char const*
constructor overload, which would call __builtin_strlen on the string.
Since we now have operator ""sv, we can replace these with much simpler
versions. This opens the door to being able to remove
StringView(char const*).

No functional changes.

Userland/Applications/PixelPaint/PaletteWidget.cpp

@@ -264,7 +264,7 @@ Result<void, String> PaletteWidget::save_palette_file(Vector<Color> palette, Cor
 {
     for (auto& color : palette) {
         file.write(color.to_string_without_alpha());
-        file.write("\n");
+        file.write("\n"sv);
     }
     return {};
 }