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>

tools/unencrypted-keys-gen/main.go

@@ -37,11 +37,12 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
-	defer func() {
+	cleanup := func() {
 		if err := file.Close(); err != nil {
 			log.Fatal(err)
 		}
-	}()
+	}
+	defer cleanup()
 
 	var ctnr *keygen.UnencryptedKeysContainer
 	if *random {
@@ -50,6 +51,8 @@ func main() {
 		ctnr = generateUnencryptedKeys(*startIndex)
 	}
 	if err := keygen.SaveUnencryptedKeysToFile(file, ctnr); err != nil {
+		// log.Fatal will prevent defer from being called
+		cleanup()
 		log.Fatal(err)
 	}
 }