CI: enable 32bit build on CI

[simonjayhawkins]

the number of failures on the 32bit build on https://github.com/MacPython/pandas-wheels is starting to accumulate

we should consider having a 32bit build on CI to catch these earlier (and can be addressed by the people more familiar with the changes)

a snapshot of the failures on linux py_3.8_32

=========================== short test summary info ============================
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/arrays/floating/test_function.py::test_stat_method[var-kwargs1]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/arrays/floating/test_function.py::test_stat_method[var-kwargs0]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/arrays/floating/test_function.py::test_stat_method[kurtosis-kwargs2]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/arrays/floating/test_function.py::test_stat_method[sem-kwargs4]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/base/test_misc.py::test_memory_usage[series-with-empty-index]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/groupby/test_groupby.py::test_groupby_nat_exclude
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/io/formats/test_info.py::test_info_int_columns
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/io/parser/test_c_parser_only.py::test_float_precision_options[c_high]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/io/parser/test_c_parser_only.py::test_float_precision_options[c_low]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/reshape/test_pivot.py::TestPivot::test_pivot_empty
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/window/test_rolling.py::test_rolling_var_numerical_issues[var-1-values0]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/window/test_rolling.py::test_rolling_var_numerical_issues[std-1-values1]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/window/test_rolling.py::test_rolling_var_numerical_issues[var-2-values2]
FAILED ../../venv/lib/python3.8/site-packages/pandas/tests/window/test_rolling.py::test_rolling_var_numerical_issues[std-2-values3]
= 14 failed, 80215 passed, 16918 skipped, 1380 xfailed, 13 warnings in 528.07s (0:08:48) =

#37398, #36662 and #36429 address some of these.

[fangchenli]

#35898 is working but I haven't got time to integrate it with our ci setup.

[simonjayhawkins]

closing as duplicate of #32709