ENH: Accept no fields for groupby by #22576

Job	Run time
Pyodide build	1h 7m 42s
Linux-32-bit	34m 35s
Linux-Musl	35m 46s
python-dev (macOS-13)	35m 38s
python-dev (macOS-14)	21m 4s
python-dev (ubuntu-22.04)	36m 38s
python-dev (windows-latest)	41m 42s
python-freethreading	49m 0s
macos-13 actions-310.yaml	1h 12m 14s
macos-13 actions-311.yaml	58m 48s
macos-13 actions-312.yaml	1h 30m 49s
macos-14 actions-310.yaml	56m 31s
macos-14 actions-311.yaml	46m 0s
macos-14 actions-312.yaml	40m 9s
windows-latest actions-311.yaml	1h 21m 43s
windows-latest actions-310.yaml	1h 19m 42s
windows-latest actions-312.yaml	1h 30m 16s
Minimum Versions	53m 35s
Future infer strings (without pyarrow)	1h 22m 32s
Locale: zh_CN	1h 7m 7s
Locale: it_IT	1h 8m 15s
Downstream Compat	6m 30s
Numpy Dev	41m 38s
Pyarrow Nightly	47m 15s
Pypy	1m 41s
Future infer strings	1h 30m 19s
ubuntu-22.04 actions-310.yaml	1h 30m 20s
ubuntu-22.04 actions-311.yaml	1h 30m 20s
ubuntu-22.04 actions-312.yaml	1h 30m 22s
ubuntu-24.04-arm actions-311.yaml	1h 3m 33s
ubuntu-24.04-arm actions-312.yaml	1h 30m 20s
ubuntu-24.04-arm actions-310.yaml	1h 29m 53s
	1d 7h 51m 57s

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