src: add NativeKeyObject base class

             +---------------------+
             |     BaseObject      |
             +---------------------+
                        |
                        |
                        |
             +---------------------+
             |   NativeKeyObject   |
             +---------------------+
                        |
                        |
                        |
             +---------------------+
             |      KeyObject      |
             +---------------------+
               /                 \
              /                   \
             /                     \
            /                       \
+---------------------+    +---------------------+
|   SecretKeyObject   |    | AsymmetricKeyObject |
+---------------------+    +---------------------+
                             /                 \
                            /                   \
                           /                     \
                          /                       \
              +---------------------+   +---------------------+
              |   PublicKeyObject   |   |   PrivateKeyObject  |
              +---------------------+   +---------------------+

PR-URL: https://github.com/nodejs/node/pull/33360


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>