[chore] Do not introduce pointers in the deprecated batcher fields

Do not introduce an unnecessary Go API breaking change

Author: dmitryax

exporter/exporterbatcher/config.go

@@ -42,26 +42,26 @@ type SizeConfig struct {
 // Deprecated: [v0.121.0] use SizeConfig.
 type MinSizeConfig struct {
 	// Deprecated: [v0.121.0] use SizeConfig.MinSize.
-	MinSizeItems *int `mapstructure:"min_size_items"`
+	MinSizeItems int `mapstructure:"min_size_items"`
 }
 
 // Deprecated: [v0.121.0] use SizeConfig.
 type MaxSizeConfig struct {
 	// Deprecated: [v0.121.0] use SizeConfig.MaxSize.
-	MaxSizeItems *int `mapstructure:"max_size_items"`
+	MaxSizeItems int `mapstructure:"max_size_items"`
 }
 
 func (c *Config) Unmarshal(conf *confmap.Conf) error {
 	if err := conf.Unmarshal(c); err != nil {
 		return err
 	}
 
-	if c.MinSizeItems != nil {
-		c.SizeConfig.MinSize = *c.MinSizeItems
+	if conf.IsSet("min_size_items") {
+		c.SizeConfig.MinSize = c.MinSizeItems
 	}
 
-	if c.MaxSizeItems != nil {
-		c.SizeConfig.MaxSize = *c.MaxSizeItems
+	if conf.IsSet("max_size_items") {
+		c.SizeConfig.MaxSize = c.MaxSizeItems
 	}
 
 	return nil

exporter/exporterbatcher/config_test.go

@@ -7,6 +7,8 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/confmap"
 )
 
 func TestValidateConfig(t *testing.T) {
@@ -40,3 +42,29 @@ func TestValidateSizeConfig(t *testing.T) {
 	}
 	require.EqualError(t, cfg.Validate(), "`max_size` must be greater than or equal to mix_size")
 }
+
+func TestUnmarshalDeprecatedConfig(t *testing.T) {
+	cfg := NewDefaultConfig()
+	require.NoError(t, cfg.Unmarshal(confmap.NewFromStringMap(map[string]any{
+		"enabled":        true,
+		"flush_timeout":  200,
+		"min_size_items": 111,
+		"max_size_items": 222,
+	})))
+	require.NoError(t, cfg.Validate())
+	require.Equal(t, cfg, Config{
+		Enabled:      true,
+		FlushTimeout: 200,
+		SizeConfig: SizeConfig{
+			Sizer:   SizerTypeItems,
+			MinSize: 111,
+			MaxSize: 222,
+		},
+		MinSizeConfig: MinSizeConfig{
+			MinSizeItems: 111,
+		},
+		MaxSizeConfig: MaxSizeConfig{
+			MaxSizeItems: 222,
+		},
+	})
+}