perf: use new PyLong* API for num-bigint feature

[chirizxc]

Related: #6040

See codspeed comment for benchmark improvements.

[codspeed-hq]

Merging this PR will improve performance by 86.02%

⚡ 17 improved benchmarks
❌ 1 regressed benchmark
✅ 122 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	into_u128_u64_max	1.5 µs	2 µs	-26.2%
⚡	into_bigint_huge_negative	23.4 µs	6.6 µs	×3.5
⚡	extract_biguint_negative_fail	7.3 µs	2.3 µs	×3.2
⚡	extract_biguint_zero	2,700.6 ns	916.9 ns	×2.9
⚡	into_bigint_huge_positive	17.3 µs	6.6 µs	×2.6
⚡	into_biguint_huge	17 µs	6.6 µs	×2.6
⚡	into_bigint_big_negative	5.2 µs	2.1 µs	×2.4
⚡	into_bigint_big_positive	4.4 µs	2.1 µs	×2.1
⚡	into_bigint_small	3.1 µs	1.5 µs	×2.1
⚡	into_biguint_big	4.3 µs	2.1 µs	+98.96%
⚡	into_biguint_small	3.3 µs	2 µs	+66.96%
⚡	extract_biguint_small	2.6 µs	1.6 µs	+56.78%
⚡	extract_bigint_small	2.7 µs	1.7 µs	+56.11%
⚡	extract_bigint_huge_negative	13 µs	8.5 µs	+52.2%
⚡	into_biguint_zero	2.8 µs	2 µs	+44.16%
⚡	extract_biguint_huge	11 µs	7.8 µs	+41.24%
⚡	extract_bigint_huge_positive	11.7 µs	8.5 µs	+37.62%
⚡	extract_bigint_big_negative	3.9 µs	3.4 µs	+16.32%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing chirizxc:PyLongForBigInt (9584a53) with main (b3aa7da)}

[davidhewitt]

Thanks, generally looks good on the from-python implementation; I think possible gains yet to be had in the to-python implementation.

[davidhewitt]

Some observations on this path:

• I would prefer to have this logic extracted into a generic function; I think it's easier to maintain than when it's deeply nested inside a macro.
• I think we can avoid the intermediate Vec allocation from the digits and instead wrap the iterator coming out of the big-integer. pylong_from_digits needs an ExactSizeIterator, so it'll be a touch fiddly but I think still possible.
• I think we lack benchmarks for the bigint to-python pathway, so possibly worth landing some of those before we think too hard about this.

[chirizxc]

• I think we lack benchmarks for the bigint to-python pathway, so possibly worth landing some of those before we think too hard about this.

#6148

[davidhewitt]

Also, I think worth giving this a changed newsfragment to note to users we've optimized the bigint conversions on 3.14+.

[chirizxc]

⚠️ Different runtime environments detected

How exactly are GitHub machines assigned for running jobs, is it random?

Doesn't codspeed run benchmarks on the PR and main branches? Does it benchmark only the PR for every commit and compare the results to those saved from the main branch?

I mean, is there anything that can be done about the ⚠️ Different runtime environments detected error?