Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #2807

Job	Run time
checks / pre-commit	22s
checks / readme-snippets	13s
checks / test (3.10, highest, windows-latest)	1m 10s
checks / test (3.10, lowest-direct, windows-latest)	1m 27s
checks / test (3.10, lowest-direct, ubuntu-latest)	35s
checks / test (3.11, lowest-direct, windows-latest)	1m 19s
checks / test (3.11, lowest-direct, ubuntu-latest)	34s
checks / test (3.10, highest, ubuntu-latest)	34s
checks / test (3.11, highest, ubuntu-latest)	32s
checks / test (3.12, lowest-direct, ubuntu-latest)	34s
checks / test (3.13, highest, windows-latest)	1m 18s
checks / test (3.13, lowest-direct, ubuntu-latest)	34s
checks / test (3.13, highest, ubuntu-latest)	34s
checks / test (3.11, highest, windows-latest)	1m 33s
checks / test (3.12, lowest-direct, windows-latest)	1m 30s
checks / test (3.13, lowest-direct, windows-latest)	1m 14s
checks / test (3.12, highest, windows-latest)	1m 17s
checks / test (3.12, highest, ubuntu-latest)	34s
	15m 54s

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