Refine must2 and apply NewAesGcm() to all usage (#5011)

* Refine must2 and apply NewAesGcm() to all usage

* Remove unused package

* Fix test

transport/internet/kcp/cryptreal.go

@@ -1,15 +1,13 @@
 package kcp
 
 import (
-	"crypto/aes"
 	"crypto/cipher"
 	"crypto/sha256"
 
-	"github.com/xtls/xray-core/common"
+	"github.com/xtls/xray-core/common/crypto"
 )
 
 func NewAEADAESGCMBasedOnSeed(seed string) cipher.AEAD {
 	hashedSeed := sha256.Sum256([]byte(seed))
-	aesBlock := common.Must2(aes.NewCipher(hashedSeed[:16])).(cipher.Block)
-	return common.Must2(cipher.NewGCM(aesBlock)).(cipher.AEAD)
+	return crypto.NewAesGcm(hashedSeed[:])
 }

transport/internet/reality/reality.go

@@ -3,8 +3,6 @@ package reality
 import (
 	"bytes"
 	"context"
-	"crypto/aes"
-	"crypto/cipher"
 	"crypto/ecdh"
 	"crypto/ed25519"
 	"crypto/hmac"
@@ -169,8 +167,7 @@ func UClient(c net.Conn, config *Config, ctx context.Context, dest net.Destinati
 		if _, err := hkdf.New(sha256.New, uConn.AuthKey, hello.Random[:20], []byte("REALITY")).Read(uConn.AuthKey); err != nil {
 			return nil, err
 		}
-		block, _ := aes.NewCipher(uConn.AuthKey)
-		aead, _ := cipher.NewGCM(block)
+		aead := crypto.NewAesGcm(uConn.AuthKey)
 		if config.Show {
 			fmt.Printf("REALITY localAddr: %v\tuConn.AuthKey[:16]: %v\tAEAD: %T\n", localAddr, uConn.AuthKey[:16], aead)
 		}

transport/internet/splithttp/dialer.go

@@ -297,7 +297,7 @@ func Dial(ctx context.Context, dest net.Destination, streamSettings *internet.Me
 	if transportConfiguration.DownloadSettings != nil {
 		globalDialerAccess.Lock()
 		if streamSettings.DownloadSettings == nil {
-			streamSettings.DownloadSettings = common.Must2(internet.ToMemoryStreamConfig(transportConfiguration.DownloadSettings)).(*internet.MemoryStreamConfig)
+			streamSettings.DownloadSettings = common.Must2(internet.ToMemoryStreamConfig(transportConfiguration.DownloadSettings))
 			if streamSettings.SocketSettings != nil && streamSettings.SocketSettings.Penetrate {
 				streamSettings.DownloadSettings.SocketSettings = streamSettings.SocketSettings
 			}