fix: Fix too many cluster columns requested by caching

[TrevorBergeron]

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Fixes #<issue_number_goes_here> 🦕

[tswast]

Test failure:

================================== FAILURES ===================================
________________________ test_df_cached_many_index_cols ________________________
[gw17] linux -- Python 3.9.20 /tmpfs/src/github/python-bigquery-dataframes/.nox/system-3-9/bin/python

scalars_df_index =           bool_col                                          bytes_col  \
rowindex                                     ...99999+00:00     0:00:00.000004  
8                                     <NA>    5 days, 0:00:00  

[9 rows x 14 columns]

    def test_df_cached_many_index_cols(scalars_df_index):
        index_cols = [
            "int64_too",
            "geography_col",
            "int64_col",
            "bool_col",
            "date_col",
            "timestamp_col",
            "string_col",
        ]
        df = scalars_df_index.set_index(index_cols)
        df = df[df["rowindex_2"] % 2 == 0]
    
        df_cached_copy = df.cache()
>       pandas.testing.assert_frame_equal(df.to_pandas(), df_cached_copy.to_pandas())

[tests/system/small/test_dataframe.py:5554](https://cs.corp.google.com/piper///depot/google3/tests/system/small/test_dataframe.py?l=5554): 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
[bigframes/core/log_adapter.py:195](https://cs.corp.google.com/piper///depot/google3/bigframes/core/log_adapter.py?l=195): in wrapper
    raise e
[bigframes/core/log_adapter.py:180](https://cs.corp.google.com/piper///depot/google3/bigframes/core/log_adapter.py?l=180): in wrapper
    return method(*args, **kwargs)
[bigframes/dataframe.py:1870](https://cs.corp.google.com/piper///depot/google3/bigframes/dataframe.py?l=1870): in to_pandas
    df, query_job = self._block.to_pandas(
[bigframes/core/blocks.py:647](https://cs.corp.google.com/piper///depot/google3/bigframes/core/blocks.py?l=647): in to_pandas
    df = self._copy_index_to_pandas(df)
[bigframes/core/blocks.py:747](https://cs.corp.google.com/piper///depot/google3/bigframes/core/blocks.py?l=747): in _copy_index_to_pandas
    new_df.set_index(list(self.index_columns), inplace=True)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/util/_decorators.py:331](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/util/_decorators.py?l=331): in wrapper
    return func(*args, **kwargs)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/frame.py:6067](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/frame.py?l=6067): in set_index
    index = ensure_index_from_sequences(arrays, names)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/indexes/base.py:7274](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/indexes/base.py?l=7274): in ensure_index_from_sequences
    return MultiIndex.from_arrays(sequences, names=names)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/indexes/multi.py:489](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/indexes/multi.py?l=489): in from_arrays
    codes, levels = factorize_from_iterables(arrays)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/arrays/categorical.py:3007](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/arrays/categorical.py?l=3007): in factorize_from_iterables
    codes, categories = zip(*(factorize_from_iterable(it) for it in iterables))
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/arrays/categorical.py:3007](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/arrays/categorical.py?l=3007): in <genexpr>
    codes, categories = zip(*(factorize_from_iterable(it) for it in iterables))
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/arrays/categorical.py:2980](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/arrays/categorical.py?l=2980): in factorize_from_iterable
    cat = Categorical(values, ordered=False)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/arrays/categorical.py:454](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/arrays/categorical.py?l=454): in __init__
    dtype = CategoricalDtype(categories, dtype.ordered)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/dtypes/dtypes.py:186](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/dtypes/dtypes.py?l=186): in __init__
    self._finalize(categories, ordered, fastpath=False)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/dtypes/dtypes.py:340](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/dtypes/dtypes.py?l=340): in _finalize
    categories = self.validate_categories(categories, fastpath=fastpath)
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/dtypes/dtypes.py:536](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/dtypes/dtypes.py?l=536): in validate_categories
    if not categories.is_unique:
[pandas/_libs/properties.pyx:36](https://cs.corp.google.com/piper///depot/google3/pandas/_libs/properties.pyx?l=36): in pandas._libs.properties.CachedProperty.__get__
    ???
[.nox/system-3-9/lib/python3.9/site-packages/pandas/core/indexes/base.py:2386](https://cs.corp.google.com/piper///depot/google3/.nox/system-3-9/lib/python3.9/site-packages/pandas/core/indexes/base.py?l=2386): in is_unique
    return self._engine.is_unique
[pandas/_libs/index.pyx:225](https://cs.corp.google.com/piper///depot/google3/pandas/_libs/index.pyx?l=225): in pandas._libs.index.IndexEngine.is_unique.__get__
    ???
[pandas/_libs/index.pyx:232](https://cs.corp.google.com/piper///depot/google3/pandas/_libs/index.pyx?l=232): in pandas._libs.index.IndexEngine._do_unique_check
    ???
[pandas/_libs/index.pyx:290](https://cs.corp.google.com/piper///depot/google3/pandas/_libs/index.pyx?l=290): in pandas._libs.index.IndexEngine._ensure_mapping_populated
    ???
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

>   ???
E   TypeError: unhashable type: 'Point'

[pandas/_libs/hashtable_class_helper.pxi:5778](https://cs.corp.google.com/piper///depot/google3/pandas/_libs/hashtable_class_helper.pxi?l=5778): TypeError