Add more logs in bootstrap generator (#6507)

## Motivation

Increase bootstrapper verbosity for a better understanding of what it does.

bootstrap/types.go

@@ -21,6 +21,13 @@ type EpochData struct {
 	ActiveSet []string `json:"activeSet"`
 }
 
+func (ed *EpochData) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
+	encoder.AddUint32("epoch", ed.ID)
+	encoder.AddString("beacon", ed.Beacon)
+	encoder.AddInt("activeset_size", len(ed.ActiveSet))
+	return nil
+}
+
 type VerifiedUpdate struct {
 	Data      *EpochOverride
 	Persisted string

cmd/bootstrapper/generator.go

@@ -107,12 +107,14 @@ func (g *Generator) Generate(
 	}
 
 	if genBeacon {
+		g.logger.Info("bootstrapping beacon", zap.Uint32("epoch", targetEpoch.Uint32()))
 		beacon, err = g.genBeacon(ctx, g.logger)
 		if err != nil {
 			return "", err
 		}
 	}
 	if genActiveSet {
+		g.logger.Info("bootstrapping activeset", zap.Uint32("epoch", targetEpoch.Uint32()))
 		activeSet, err = getActiveSet(ctx, g.smEndpoint, targetEpoch-1)
 		if err != nil {
 			return "", err
@@ -245,6 +247,7 @@ func (g *Generator) GenUpdate(
 	if len(activeSet) > 0 {
 		edata.ActiveSet = as
 	}
+	g.logger.Info("generated bootstrap", zap.Inline(&edata))
 	update.Data = bootstrap.InnerData{
 		Epoch: edata,
 	}
@@ -261,8 +264,6 @@ func (g *Generator) GenUpdate(
 	if err != nil {
 		return "", fmt.Errorf("persist epoch update %v: %w", filename, err)
 	}
-	g.logger.Info("generated update",
-		zap.String("filename", filename),
-	)
+	g.logger.Info("generated update", zap.String("filename", filename))
 	return filename, nil
 }