Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #3823

Job	Run time
checks / readme-snippets	14s
checks / pre-commit	37s
checks / test (3.10, lowest-direct, windows-latest)	2m 35s
checks / test (3.11, lowest-direct, windows-latest)	2m 24s
checks / test (3.12, lowest-direct, ubuntu-latest)	52s
checks / test (3.10, highest, windows-latest)	2m 25s
checks / test (3.11, lowest-direct, ubuntu-latest)	44s
checks / test (3.10, lowest-direct, ubuntu-latest)	46s
checks / test (3.11, highest, ubuntu-latest)	48s
checks / test (3.10, highest, ubuntu-latest)	46s
checks / test (3.11, highest, windows-latest)	2m 26s
checks / test (3.13, highest, ubuntu-latest)	47s
checks / test (3.12, highest, ubuntu-latest)	53s
checks / test (3.12, highest, windows-latest)	3m 23s
checks / test (3.13, lowest-direct, ubuntu-latest)	46s
checks / test (3.12, lowest-direct, windows-latest)	3m 32s
checks / test (3.13, lowest-direct, windows-latest)	2m 26s
checks / test (3.13, highest, windows-latest)	2m 38s
	29m 2s

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