feat(cloudrequestlog): use slog.Level for config values

The string values are equivalent (debug/info/warn/error) across zap and
slog, so although this is technically a breaking change, the risk of
breakage is small, and the migration if it happens is simple.

cloudrequestlog/config.go

@@ -1,7 +1,8 @@
 package cloudrequestlog
 
 import (
-	"go.uber.org/zap/zapcore"
+	"log/slog"
+
 	"google.golang.org/grpc/codes"
 )
 
@@ -12,7 +13,7 @@ type Config struct {
 	// Default value, 0, means that no messages will be truncated.
 	MessageSizeLimit int `onGCE:"1024"`
 	// CodeToLevel enables overriding the default gRPC code to level conversion.
-	CodeToLevel map[codes.Code]zapcore.Level
+	CodeToLevel map[codes.Code]slog.Level
 	// StatusToLevel enables overriding the default HTTP status code to level conversion.
-	StatusToLevel map[int]zapcore.Level
+	StatusToLevel map[int]slog.Level
 }

cloudrequestlog/middleware.go

@@ -254,14 +254,14 @@ func (l *Middleware) applyMessageTransform(message proto.Message) proto.Message
 
 func (l *Middleware) codeToLevel(code codes.Code) zapcore.Level {
 	if level, ok := l.Config.CodeToLevel[code]; ok {
-		return level
+		return slogToLevel(level)
 	}
 	return CodeToLevel(code)
 }
 
 func (l *Middleware) statusToLevel(status int) zapcore.Level {
 	if level, ok := l.Config.StatusToLevel[status]; ok {
-		return level
+		return slogToLevel(level)
 	}
 	switch {
 	case status < http.StatusBadRequest: