tls: tls_wrap causes debug assert in vector

When using a debug build (on Windows specifically) the error case for
tls_wrap causes an assert to fire because the index being passed is
outside the bounds of the vector.

The fix is to switch to iterators.

PR-URL: nodejs#18830
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/tls_wrap.cc

@@ -491,8 +491,8 @@ bool TLSWrap::ClearIn() {
     // This can be skipped in the error case because no further writes
     // would succeed anyway.
     pending_cleartext_input_.insert(pending_cleartext_input_.end(),
-                                    &buffers[i],
-                                    &buffers[buffers.size()]);
+                                    buffers.begin() + i,
+                                    buffers.end());
   }
 
   return false;