Logrus hooks for terminal vs log-file output (#16102)

## Review after #16059 

**What type of PR is this?**
Feature

**What does this PR do?**
This PR introduces logrus writer hooks into the logging of prysm.
when log-format is text:
- set the default logrus output to be `io.Discard`
- create a writer hook for terminal, with formatting and coloring
enabled.
- create a separate writer hook for log-file (if enabled), without
coloring.

This immediately allows for having formatted/colored terminal logs,
while keeping the log-file clean.

cmd/beacon-chain/main.go

@@ -4,6 +4,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 	runtimeDebug "runtime/debug"
@@ -172,14 +173,20 @@ func before(ctx *cli.Context) error {
 
 	switch format {
 	case "text":
+		// disabling logrus default output so we can control it via different hooks
+		logrus.SetOutput(io.Discard)
+
+		// create a custom formatter and hook for terminal output
 		formatter := new(prefixed.TextFormatter)
 		formatter.TimestampFormat = "2006-01-02 15:04:05.00"
 		formatter.FullTimestamp = true
+		formatter.ForceFormatting = true
+		formatter.ForceColors = true
 
-		// If persistent log files are written - we disable the log messages coloring because
-		// the colors are ANSI codes and seen as gibberish in the log files.
-		formatter.DisableColors = ctx.String(cmd.LogFileName.Name) != ""
-		logrus.SetFormatter(formatter)
+		logrus.AddHook(&logs.WriterHook{
+			Formatter: formatter,
+			Writer:    os.Stderr,
+		})
 	case "fluentd":
 		f := joonix.NewFormatter()
 
@@ -202,7 +209,7 @@ func before(ctx *cli.Context) error {
 
 	logFileName := ctx.String(cmd.LogFileName.Name)
 	if logFileName != "" {
-		if err := logs.ConfigurePersistentLogging(logFileName); err != nil {
+		if err := logs.ConfigurePersistentLogging(logFileName, format); err != nil {
 			log.WithError(err).Error("Failed to configuring logging to disk.")
 		}
 	}

cmd/client-stats/main.go

@@ -86,7 +86,7 @@ func main() {
 
 		logFileName := ctx.String(cmd.LogFileName.Name)
 		if logFileName != "" {
-			if err := logs.ConfigurePersistentLogging(logFileName); err != nil {
+			if err := logs.ConfigurePersistentLogging(logFileName, format); err != nil {
 				log.WithError(err).Error("Failed to configuring logging to disk.")
 			}
 		}

cmd/validator/main.go

@@ -5,6 +5,7 @@ package main
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 	runtimeDebug "runtime/debug"
@@ -151,13 +152,20 @@ func main() {
 			format := ctx.String(cmd.LogFormat.Name)
 			switch format {
 			case "text":
+				// disabling logrus default output so we can control it via different hooks
+				logrus.SetOutput(io.Discard)
+
+				// create a custom formatter and hook for terminal output
 				formatter := new(prefixed.TextFormatter)
 				formatter.TimestampFormat = "2006-01-02 15:04:05.00"
 				formatter.FullTimestamp = true
-				// If persistent log files are written - we disable the log messages coloring because
-				// the colors are ANSI codes and seen as gibberish in the log files.
-				formatter.DisableColors = logFileName != ""
-				logrus.SetFormatter(formatter)
+				formatter.ForceFormatting = true
+				formatter.ForceColors = true
+
+				logrus.AddHook(&logs.WriterHook{
+					Formatter: formatter,
+					Writer:    os.Stderr,
+				})
 			case "fluentd":
 				f := joonix.NewFormatter()
 				if err := joonix.DisableTimestampFormat(f); err != nil {
@@ -177,7 +185,7 @@ func main() {
 			}
 
 			if logFileName != "" {
-				if err := logs.ConfigurePersistentLogging(logFileName); err != nil {
+				if err := logs.ConfigurePersistentLogging(logFileName, format); err != nil {
 					log.WithError(err).Error("Failed to configuring logging to disk.")
 				}
 			}