Replace httpx and httpx-sse with httpx2 #3209

Job	Run time
checks / pre-commit	53s
checks / readme-snippets	12s
checks / docs	43s
checks / test (3.10, lowest-direct, windows-latest)	1m 52s
checks / test (3.11, locked, windows-latest)	1m 45s
checks / test (3.10, locked, windows-latest)	2m 0s
checks / test (3.11, locked, ubuntu-latest)	1m 15s
checks / test (3.11, lowest-direct, windows-latest)	1m 36s
checks / test (3.14, locked, ubuntu-latest)	2m 17s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 24s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 14s
checks / test (3.10, locked, ubuntu-latest)	1m 17s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 17s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 4s
checks / test (3.14, lowest-direct, windows-latest)	1m 49s
checks / test (3.13, lowest-direct, windows-latest)	2m 32s
checks / test (3.12, locked, windows-latest)	2m 0s
checks / test (3.13, locked, ubuntu-latest)	1m 10s
checks / test (3.13, locked, windows-latest)	1m 41s
checks / test (3.14, locked, windows-latest)	2m 25s
checks / test (3.12, locked, ubuntu-latest)	1m 27s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 8s
checks / test (3.12, lowest-direct, windows-latest)	1m 50s
all-green	3s
	34m 54s

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