feat: RESP3 notifications support & Hitless notifications handling [CAE-1088] & [CAE-1072] (#3418)

- Adds support for handling push notifications with RESP3. 
- Using this support adds handlers for hitless upgrades.

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Hristo Temelski <hristo.temelski@redis.com>

hitless/hooks.go

@@ -0,0 +1,47 @@
+package hitless
+
+import (
+	"context"
+
+	"github.com/redis/go-redis/v9/internal"
+	"github.com/redis/go-redis/v9/internal/pool"
+	"github.com/redis/go-redis/v9/logging"
+	"github.com/redis/go-redis/v9/push"
+)
+
+// LoggingHook is an example hook implementation that logs all notifications.
+type LoggingHook struct {
+	LogLevel logging.LogLevel
+}
+
+// PreHook logs the notification before processing and allows modification.
+func (lh *LoggingHook) PreHook(ctx context.Context, notificationCtx push.NotificationHandlerContext, notificationType string, notification []interface{}) ([]interface{}, bool) {
+	if lh.LogLevel.InfoOrAbove() { // Info level
+		// Log the notification type and content
+		connID := uint64(0)
+		if conn, ok := notificationCtx.Conn.(*pool.Conn); ok {
+			connID = conn.GetID()
+		}
+		internal.Logger.Printf(ctx, "hitless: conn[%d] processing %s notification: %v", connID, notificationType, notification)
+	}
+	return notification, true // Continue processing with unmodified notification
+}
+
+// PostHook logs the result after processing.
+func (lh *LoggingHook) PostHook(ctx context.Context, notificationCtx push.NotificationHandlerContext, notificationType string, notification []interface{}, result error) {
+	connID := uint64(0)
+	if conn, ok := notificationCtx.Conn.(*pool.Conn); ok {
+		connID = conn.GetID()
+	}
+	if result != nil && lh.LogLevel.WarnOrAbove() { // Warning level
+		internal.Logger.Printf(ctx, "hitless: conn[%d] %s notification processing failed: %v - %v", connID, notificationType, result, notification)
+	} else if lh.LogLevel.DebugOrAbove() { // Debug level
+		internal.Logger.Printf(ctx, "hitless: conn[%d] %s notification processed successfully", connID, notificationType)
+	}
+}
+
+// NewLoggingHook creates a new logging hook with the specified log level.
+// Log levels: LogLevelError=errors, LogLevelWarn=warnings, LogLevelInfo=info, LogLevelDebug=debug
+func NewLoggingHook(logLevel logging.LogLevel) *LoggingHook {
+	return &LoggingHook{LogLevel: logLevel}
+}