Python 3.9 does not support `int.is_integer()`

[sjmonson]

Versions of python older than 3.12 do not support int.is_integer() which can happen when --rate is called with a whole number:

Traceback (most recent call last):
  File "/opt/app-root/bin/guidellm", line 8, in <module>
    sys.exit(cli())
             ^^^^^
  File "/opt/app-root/lib64/python3.11/site-packages/click/core.py", line 1161, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/app-root/lib64/python3.11/site-packages/click/core.py", line 1082, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/opt/app-root/lib64/python3.11/site-packages/click/core.py", line 1697, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/app-root/lib64/python3.11/site-packages/click/core.py", line 1443, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/app-root/lib64/python3.11/site-packages/click/core.py", line 788, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/app-root/src/guidellm/src/guidellm/__main__.py", line 255, in benchmark
    asyncio.run(
  File "/usr/lib64/python3.11/asyncio/runners.py", line 190, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/asyncio/base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/opt/app-root/src/guidellm/src/guidellm/benchmark/entrypoints.py", line 88, in benchmark_generative_text
    profile = create_profile(rate_type=rate_type, rate=rate)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/app-root/src/guidellm/src/guidellm/benchmark/profile.py", line 380, in create_profile
    return ConcurrentProfile.from_standard_args(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/app-root/src/guidellm/src/guidellm/benchmark/profile.py", line 138, in from_standard_args
    if not all(stream.is_integer() and stream > 0 for stream in rate):
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/app-root/src/guidellm/src/guidellm/benchmark/profile.py", line 138, in <genexpr>
    if not all(stream.is_integer() and stream > 0 for stream in rate):
               ^^^^^^^^^^^^^^^^^
AttributeError: 'int' object has no attribute 'is_integer'