TST: Add test for groupby with datetime and NaT values #22180

Job	Run time
Pyodide build	23m 21s
Linux-32-bit	18m 16s
Linux-Musl	16m 39s
python-freethreading	23m 28s
python-dev (macOS-13)	21m 48s
python-dev (macOS-14)	17m 47s
python-dev (ubuntu-22.04)	20m 13s
macos-13 actions-310.yaml	29m 40s
macos-13 actions-311.yaml	27m 6s
python-dev (windows-latest)	22m 37s
macos-13 actions-312.yaml	28m 6s
macos-14 actions-310.yaml	25m 29s
macos-14 actions-311.yaml	13m 58s
macos-14 actions-312.yaml	19m 42s
windows-latest actions-311.yaml	37m 12s
windows-latest actions-312.yaml	48m 3s
windows-latest actions-310.yaml	34m 55s
Minimum Versions	23m 1s
Future infer strings (without pyarrow)	41m 6s
Locale: zh_CN	23m 55s
Locale: it_IT	23m 3s
Downstream Compat	5m 44s
Numpy Dev	16m 43s
Pyarrow Nightly	20m 13s
Future infer strings	50m 11s
Pypy	1m 16s
ubuntu-22.04 actions-310.yaml	47m 52s
ubuntu-22.04 actions-311.yaml	44m 36s
ubuntu-22.04 actions-312.yaml	49m 29s
ubuntu-24.04-arm actions-311.yaml	40m 7s
ubuntu-24.04-arm actions-312.yaml	43m 3s
ubuntu-24.04-arm actions-310.yaml	40m 45s
	14h 59m 24s

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