ENH: Add Rolling.nunique() #22364

Job	Run time
Linux-Musl	16m 15s
Pyodide build	23m 19s
Linux-32-bit	18m 24s
python-freethreading	22m 34s
python-dev (macOS-13)	21m 36s
python-dev (macOS-14)	10m 26s
python-dev (ubuntu-22.04)	20m 13s
python-dev (windows-latest)	22m 21s
macos-13 actions-310.yaml	22m 31s
macos-13 actions-311.yaml	23m 26s
macos-14 actions-310.yaml	15m 56s
macos-13 actions-312.yaml	29m 33s
macos-14 actions-311.yaml	17m 59s
macos-14 actions-312.yaml	18m 2s
windows-latest actions-311.yaml	43m 26s
windows-latest actions-312.yaml	57m 30s
windows-latest actions-310.yaml	40m 17s
Minimum Versions	23m 10s
Future infer strings (without pyarrow)	40m 33s
Locale: zh_CN	22m 53s
Downstream Compat	5m 39s
Locale: it_IT	23m 13s
Pyarrow Nightly	20m 18s
Numpy Dev	16m 36s
Pypy	1m 24s
Future infer strings	47m 36s
ubuntu-22.04 actions-310.yaml	47m 46s
ubuntu-22.04 actions-311.yaml	43m 48s
ubuntu-22.04 actions-312.yaml	48m 11s
ubuntu-24.04-arm actions-311.yaml	37m 35s
ubuntu-24.04-arm actions-310.yaml	41m 35s
ubuntu-24.04-arm actions-312.yaml	48m 4s
	14h 52m 9s

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