DEV: Unify code between PdfReader and PdfWriter #4442

Job	Run time
Check code style issues	42s
Check code style issues	37s
pytest on 3.7 (crypto-lib: cryptography)	3m 37s
pytest on 3.7 (crypto-lib: cryptography)	3m 37s
pytest on 3.8 (crypto-lib: cryptography)	3m 49s
pytest on 3.8 (crypto-lib: cryptography)	3m 49s
Build & verify package	10s
Build & verify package	10s
pytest on 3.9 (crypto-lib: cryptography)	3m 50s
pytest on 3.9 (crypto-lib: cryptography)	3m 50s
pytest on windows	4m 55s
pytest on windows	4m 55s
pytest on 3.10 (crypto-lib: cryptography)	3m 48s
pytest on 3.10 (crypto-lib: cryptography)	3m 48s
pytest on 3.11 (crypto-lib: cryptography)	3m 22s
pytest on 3.11 (crypto-lib: cryptography)	3m 22s
pytest on 3.12 (crypto-lib: cryptography)	4m 59s
pytest on 3.12 (crypto-lib: cryptography)	4m 59s
pytest on 3.7 (crypto-lib: pycryptodome)	3m 31s
pytest on 3.7 (crypto-lib: pycryptodome)	3m 31s
pytest on 3.7 (crypto-lib: none)	3m 45s
pytest on 3.7 (crypto-lib: none)	3m 45s
Combine & check coverage.	15s
Combine & check coverage.	15s
	1h 13m 21s

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