Get rid of --add-opens workaround, and turn it into a modifier shipped with running-ng

[caizixian]

It's currently not sufficient.

  h2o21:
    type: JVMArg
    val: "-Dsys.ai.h2o.debug.allowJavaVersions=21 --add-opens java.base/java.lang=ALL-UNNAMED"
    includes:
      dacapochopin-rc5:
        - h2o
  cassandra21:
    type: JVMArg
    val: "-Djava.security.manager=allow --add-exports java.base/sun.nio.ch=ALL-UNNAMED --add-opens java.base/java.io=ALL-UNNAMED --add-opens java.base/sun.nio.ch=ALL-UNNAMED"
    includes:
      dacapochopin-rc5:
        - cassandra
  trades21:
    type: JVMArg
    val: "--add-opens java.base/java.util=ALL-UNNAMED"
    includes:
      dacapochopin-rc5:
        - tradebeans
        - tradesoap

[caizixian]

Partially resolved in #131. #114 is probably not needed anymore. Encoding such complicated workaround in the code is a bad idea, and it cannot be easily customized by users.