[backport 2.3.x] TST (string dtype): resolve xfails for frame fillna and replace tests + fix bug in replace for string (#60295) #21091

Job	Run time
Linux-32-bit	18m 44s
Linux-Musl	22m 5s
python-dev (macOS-13)	22m 25s
python-dev (macOS-14)	13m 1s
python-dev (ubuntu-22.04)	25m 21s
macos-13 actions-310.yaml	31m 34s
macos-13 actions-311.yaml	33m 43s
python-dev (windows-latest)	26m 0s
macos-13 actions-312.yaml	38m 34s
macos-13 actions-39.yaml	36m 1s
macos-14 actions-310.yaml	19m 42s
macos-14 actions-311.yaml	24m 14s
macos-14 actions-312.yaml	22m 29s
macos-14 actions-39.yaml	26m 45s
windows-latest actions-311.yaml	1h 5m 40s
windows-latest actions-312.yaml	1h 10m 14s
windows-latest actions-310.yaml	1h 4m 16s
windows-latest actions-39.yaml	37m 40s
ubuntu-latest actions-310.yaml	53m 39s
Copy-on-Write 3.10 (warnings)	29m 15s
Copy-on-Write 3.10	28m 10s
ubuntu-latest actions-311.yaml	49m 33s
Future infer strings (without pyarrow)	47m 32s
Locale: zh_CN	26m 48s
Copy-on-Write 3.11	27m 37s
Numpy Dev	22m 38s
Copy-on-Write 3.11 (warnings)	27m 15s
Locale: it_IT	27m 34s
Downstream Compat	5m 35s
Pyarrow Nightly	23m 17s
ubuntu-latest actions-312.yaml	37m 38s
Copy-on-Write 3.12	29m 44s
Future infer strings	39m 40s
ubuntu-latest actions-39.yaml	49m 15s
Copy-on-Write 3.9 (warnings)	27m 57s
Copy-on-Write 3.9	29m 9s
Minimum Versions	27m 15s
Pypy	7m 40s
	20h 15m 39s

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