refactor!: Replace `httpx` HTTP client with `impit` #342

Job	Run time
Lint check / Lint check (3.11)	11s
Lint check / Lint check (3.10)	14s
Lint check / Lint check (3.12)	9s
Type check / Type check (3.10)	17s
Type check / Type check (3.11)	19s
Async dostrings check / Async docstrings check	16s
Lint check / Lint check (3.13)	11s
Type check / Type check (3.12)	18s
Lint check / Lint check (3.9)	11s
Type check / Type check (3.9)	14s
Type check / Type check (3.13)	17s
Docs check / Docs check	1m 3s
Unit tests / Unit tests (ubuntu-latest, 3.9)	12m 14s
Unit tests / Unit tests (ubuntu-latest, 3.13)	12m 14s
Unit tests / Unit tests (ubuntu-latest, 3.11)	12m 13s
Unit tests / Unit tests (ubuntu-latest, 3.12)	12m 16s
Unit tests / Unit tests (windows-latest, 3.9)	12m 26s
Unit tests / Unit tests (ubuntu-latest, 3.10)	12m 16s
Unit tests / Unit tests (windows-latest, 3.12)	12m 36s
Unit tests / Unit tests (windows-latest, 3.10)	12m 26s
Unit tests / Unit tests (windows-latest, 3.11)	12m 28s
Unit tests / Unit tests (windows-latest, 3.13)	12m 27s
Integration tests	0s
	2h 7m 16s

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