crypto: fix misleading positional argument

The fourth positional argument of `createCipherBase` is `true` when
called from within the `Cipheriv` constructor and `false`when called
from within the `Decipheriv` constructor. This value is then passed to
the `CipherBase::New()` method, which treats it as follows:

    args[0]->IsTrue() ? kCipher : kDecipher

However, the current name of said positional argument is `decipher` and
thus indicates the exact opposite: when the argument is set to true, the
instance is *not* a `Decipheriv` object. Therefore, this commit renames
the argument to `isEncrypt`, which matches the actual semantics.

PR-URL: https://github.com/nodejs/node/pull/57843
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Edy Silva <edigleyssonsilva@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/crypto/cipher.js

@@ -112,21 +112,21 @@ function getUIntOption(options, key) {
   return -1;
 }
 
-function createCipherBase(cipher, credential, options, decipher, iv) {
+function createCipherBase(cipher, credential, options, isEncrypt, iv) {
   const authTagLength = getUIntOption(options, 'authTagLength');
-  this[kHandle] = new CipherBase(decipher);
+  this[kHandle] = new CipherBase(isEncrypt);
   this[kHandle].initiv(cipher, credential, iv, authTagLength);
   this._decoder = null;
 
   ReflectApply(LazyTransform, this, [options]);
 }
 
-function createCipherWithIV(cipher, key, options, decipher, iv) {
+function createCipherWithIV(cipher, key, options, isEncrypt, iv) {
   validateString(cipher, 'cipher');
   const encoding = getStringOption(options, 'encoding');
   key = prepareSecretKey(key, encoding);
   iv = iv === null ? null : getArrayBufferOrView(iv, 'iv');
-  ReflectApply(createCipherBase, this, [cipher, key, options, decipher, iv]);
+  ReflectApply(createCipherBase, this, [cipher, key, options, isEncrypt, iv]);
 }
 
 // The Cipher class is part of the legacy Node.js crypto API. It exposes