refactor!: Replace `httpx` HTTP client with `impit` #334

Job	Run time
Lint check / Lint check (3.12)	9s
Lint check / Lint check (3.13)	9s
Lint check / Lint check (3.11)	11s
Lint check / Lint check (3.9)	11s
Lint check / Lint check (3.10)	13s
Type check / Type check (3.12)	17s
Type check / Type check (3.9)	14s
Type check / Type check (3.10)	15s
Async dostrings check / Async docstrings check	15s
Type check / Type check (3.11)	13s
Type check / Type check (3.13)	15s
Unit tests / Unit tests (windows-latest, 3.11)	6m 47s
Unit tests / Unit tests (ubuntu-latest, 3.11)	12m 14s
Docs check / Docs check	1m 3s
Unit tests / Unit tests (windows-latest, 3.9)	6m 48s
Unit tests / Unit tests (windows-latest, 3.12)	6m 52s
Unit tests / Unit tests (ubuntu-latest, 3.12)	12m 17s
Unit tests / Unit tests (windows-latest, 3.13)	12m 34s
Unit tests / Unit tests (ubuntu-latest, 3.13)	6m 32s
Unit tests / Unit tests (windows-latest, 3.10)	12m 28s
Unit tests / Unit tests (ubuntu-latest, 3.10)	12m 16s
Unit tests / Unit tests (ubuntu-latest, 3.9)	12m 19s
Integration tests	0s
	1h 44m 32s

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