Miscellaneous code quality improvements (#7414)

* anti-patterns

* performance issues

* handle skipped defer

* gazelle fix

* misc bug risks

* make logging of proposer slashings more robust

* simplify calling span.End()

Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>

validator/client/service_test.go

@@ -57,16 +57,20 @@ func keySetup() {
 
 func TestMain(m *testing.M) {
 	dir := testutil.TempDir() + "/keystore1"
-	defer func() {
+	cleanup := func() {
 		if err := os.RemoveAll(dir); err != nil {
 			log.WithError(err).Debug("Cannot remove keystore folder")
 		}
-	}()
+	}
+	defer cleanup()
 	if err := v1.NewValidatorAccount(dir, "1234"); err != nil {
 		log.WithError(err).Debug("Cannot create validator account")
 	}
 	keySetup()
-	os.Exit(m.Run())
+	code := m.Run()
+	// os.Exit will prevent defer from being called
+	cleanup()
+	os.Exit(code)
 }
 
 func TestStop_CancelsContext(t *testing.T) {