bpo-47005: Improve performance of bytearray_repeat and bytearray_irepeat

[eendebakpt]

The bytearray_repeat and bytearray_irepeat are inefficient for small arrays and a high number of repeats.
This can be improved by using the same approach is in the corresponding bytes_repeat method.

Microbenchmarks:

python -m pyperf timeit "b=bytearray([1,2,])*100" 
python -m pyperf timeit "b=bytearray([1,2,])*1000"

Results:

Mean +- std dev: [base100] 479 ns +- 29 ns -> [patch100] 274 ns +- 18 ns: 1.75x faster
Mean +- std dev: [base1000] 2.58 us +- 0.18 us -> [patch1000] 399 ns +- 26 ns: 6.46x faster

https://bugs.python.org/issue47005

https://bugs.python.org/issue47005

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[sweeneyde]

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[methane]

Nice!