ENH: Add += and -= operators to ArrayObject #4431

Job	Run time
Check code style issues	39s
pytest on windows	4m 59s
Build & verify package	16s
pytest on 3.7 (crypto-lib: cryptography)	3m 33s
pytest on 3.8 (crypto-lib: cryptography)	3m 48s
pytest on 3.9 (crypto-lib: cryptography)	3m 44s
pytest on 3.10 (crypto-lib: cryptography)	4m 22s
pytest on 3.11 (crypto-lib: cryptography)	3m 34s
pytest on 3.12 (crypto-lib: cryptography)	4m 33s
pytest on 3.7 (crypto-lib: pycryptodome)	3m 45s
pytest on 3.7 (crypto-lib: none)	3m 53s
Combine & check coverage.	21s
	37m 27s

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