jshell does not support the --enable-native-access option

Java 17 supports the option `--enable-native-access` which allows modules to use certain new APIs from Project Panama. In order to use jshell interactively with these modules, the classes defined by jshell need this permission.

I suggest that both the /env comment and the jshell command line accept --enable-native-access (with no argument) to unlock native access.

Workaround: Use `-R--enable-native-access=ALL-UNNAMED` on the jshell command line.

For an example, please see http://cr.openjdk.java.net/~jrose/panama/argv-example.jshell