gh-101100: Fix sphinx warnings in library/resource.rst

[LamentXU123]

resource.rst:143: WARNING: py:const reference target not found: SIGXCPU [ref.const]
resource.rst:366: WARNING: py:attr reference target not found: ru_utime [ref.attr]
resource.rst:366: WARNING: py:attr reference target not found: ru_stime [ref.attr]
resource.rst:376: WARNING: py:attr reference target not found: ru_utime [ref.attr]
resource.rst:378: WARNING: py:attr reference target not found: ru_stime [ref.attr]
resource.rst:380: WARNING: py:attr reference target not found: ru_maxrss [ref.attr]
resource.rst:382: WARNING: py:attr reference target not found: ru_ixrss [ref.attr]
resource.rst:384: WARNING: py:attr reference target not found: ru_idrss [ref.attr]
resource.rst:386: WARNING: py:attr reference target not found: ru_isrss [ref.attr]
resource.rst:388: WARNING: py:attr reference target not found: ru_minflt [ref.attr]
resource.rst:390: WARNING: py:attr reference target not found: ru_majflt [ref.attr]
resource.rst:392: WARNING: py:attr reference target not found: ru_nswap [ref.attr]
resource.rst:394: WARNING: py:attr reference target not found: ru_inblock [ref.attr]
resource.rst:396: WARNING: py:attr reference target not found: ru_oublock [ref.attr]
resource.rst:398: WARNING: py:attr reference target not found: ru_msgsnd [ref.attr]
resource.rst:400: WARNING: py:attr reference target not found: ru_msgrcv [ref.attr]
resource.rst:402: WARNING: py:attr reference target not found: ru_nsignals [ref.attr]
resource.rst:404: WARNING: py:attr reference target not found: ru_nvcsw [ref.attr]
resource.rst:406: WARNING: py:attr reference target not found: ru_nivcsw [ref.attr]

• line 143. I document this in library/signal.rst

.. data:: SIGXCPU

   CPU time limit exceeded.

   .. availability:: Unix.

description and order copied from https://pubs.opengroup.org/onlinepubs/009695399/basedefs/signal.h.html

• others. They are a chart indicating attributes (served as an index) so I suppressed them

• Issue: Fix all Sphinx reference warnings in the documentation #101100

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