Deprecate and remove "Operating System Resource Limits"

From ARM:

Operating System Resource Limits
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The server's usage of many system resources can be limited. Scaled
values are allowed when specifying resource limits. For example, ``1G``
can be used instead of ``1073741824`` to specify a limit of one
gigabyte. ``unlimited`` requests unlimited use, or the maximum available
amount. ``default`` uses the limit that was in force when the server was
started. See the description of ``size_spec`` in :ref:`configuration_file_elements`.

The following options set operating system resource limits for the name
server process. Some operating systems do not support some or any of the
limits; on such systems, a warning is issued if an unsupported
limit is used.

``coresize``
   This sets the maximum size of a core dump. The default is ``default``.

``datasize``
   This sets the maximum amount of data memory the server may use. The default is
   ``default``. This is a hard limit on server memory usage; if the
   server attempts to allocate memory in excess of this limit, the
   allocation will fail, which may in turn leave the server unable to
   perform DNS service. Therefore, this option is rarely useful as a way
   to limit the amount of memory used by the server, but it can be
   used to raise an operating system data size limit that is too small
   by default. To limit the amount of memory used by the
   server, use the ``max-cache-size`` and ``recursive-clients`` options
   instead.

``files``
   This sets the maximum number of files the server may have open concurrently.
   The default is ``unlimited``.

``stacksize``
   This sets the maximum amount of stack memory the server may use. The default is
   ``default``.

These are options that are better left to be managed by the environment, and not from within the named, just deprecate these options in 9.18 and remove the options from 9.19+.