Move projectDiagnostics to it's own file and remove unused code

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

styles/src/styleTree/projectDiagnostics.ts

@@ -0,0 +1,15 @@
+import Theme from "../themes/theme";
+import {
+  backgroundColor,
+  text,
+} from "./components";
+
+export default function projectDiagnostics(theme: Theme) {
+  return {
+    background: backgroundColor(theme, 500),
+    tabIconSpacing: 4,
+    tabIconWidth: 13,
+    tabSummarySpacing: 10,
+    emptyMessage: text(theme, "sans", "secondary", { size: "md" }),
+  }
+}