crypto: add virtual dtor to KeyPairGenerationConfig

Currently the KeyPairGenerationConfigs class has a virtual function
but no virtual destructor which means that if delete is called on a
KeyPairGenerationConfig pointer to a derived instance, the derived
destructor will not get called.

The following warning is currently being printed when
compiling:

warning: delete called on 'node::crypto::KeyPairGenerationConfig' that
is abstract but has non-virtual destructor [-Wdelete-non-virtual-dtor]
    delete __ptr;

This commit adds a virtual destructor.

PR-URL: #23215
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: danbev

src/node_crypto.cc

@@ -4837,6 +4837,7 @@ class KeyPairGenerationConfig {
   virtual bool Configure(const EVPKeyCtxPointer& ctx) {
     return true;
   }
+  virtual ~KeyPairGenerationConfig() {}
 };
 
 class RSAKeyPairGenerationConfig : public KeyPairGenerationConfig {