[issue42141] Speedup various dict inits

[Marco Sulla]

Marco Sulla <launchpad.net at marco.sulla.e4ward.com> added the comment:

I'm quite sure I not invented the wheel :) but I think it's a good improvement:

| pathlib                 | 35.8 ms          | 35.1 ms            | 1.02x faster | Significant (t=13.21) |
| scimark_monte_carlo     | 176 ms           | 172 ms             | 1.02x faster | Significant (t=9.48)  |
| scimark_sor             | 332 ms           | 325 ms             | 1.02x faster | Significant (t=11.96) |
| telco                   | 11.0 ms          | 10.8 ms            | 1.03x faster | Significant (t=8.52)  |
| unpickle_pure_python    | 525 us           | 514 us             | 1.02x faster | Significant (t=19.97) |
| xml_etree_process       | 132 ms           | 129 ms             | 1.02x faster | Significant (t=17.59) |

----------
components: +Interpreter Core
type:  -> performance
versions: +Python 3.10

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue42141>
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