refactor: Enable -Wswitch in exhaustive switch

Also, apply the comment according to the dev notes.

Also, modify the dev notes to give a lambda-wrapped example.

Can be reviewed via --ignore-all-space

Co-authored-by: Lőrinc <pap.lorinc@gmail.com>

doc/developer-notes.md

@@ -854,19 +854,19 @@ Foo(vec);
 enum class Tabs {
     info,
     console,
-    network_graph,
-    peers
 };
 
 int GetInt(Tabs tab)
 {
-    switch (tab) {
-    case Tabs::info: return 0;
-    case Tabs::console: return 1;
-    case Tabs::network_graph: return 2;
-    case Tabs::peers: return 3;
-    } // no default case, so the compiler can warn about missing cases
-    assert(false);
+    int ret = [&]() {
+        switch (tab) {
+        case Tabs::info: return 0;
+        case Tabs::console: return 1;
+        } // no default case, so the compiler can warn about missing cases
+        assert(false);
+    }();
+    LogInfo("Tab %s", ret);
+    return ret;
 }
 ```