Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #3775

Job	Run time
checks / pre-commit	35s
checks / readme-snippets	11s
checks / test (3.11, lowest-direct, windows-latest)	2m 13s
checks / test (3.10, lowest-direct, windows-latest)	2m 10s
checks / test (3.10, highest, windows-latest)	2m 10s
checks / test (3.10, highest, ubuntu-latest)	46s
checks / test (3.10, lowest-direct, ubuntu-latest)	44s
checks / test (3.11, lowest-direct, ubuntu-latest)	44s
checks / test (3.11, highest, ubuntu-latest)	46s
checks / test (3.11, highest, windows-latest)	2m 41s
checks / test (3.12, highest, ubuntu-latest)	45s
checks / test (3.13, lowest-direct, ubuntu-latest)	42s
checks / test (3.12, lowest-direct, ubuntu-latest)	49s
checks / test (3.12, lowest-direct, windows-latest)	3m 19s
checks / test (3.13, highest, windows-latest)	2m 18s
checks / test (3.12, highest, windows-latest)	3m 10s
checks / test (3.13, lowest-direct, windows-latest)	2m 30s
checks / test (3.13, highest, ubuntu-latest)	42s
	27m 15s

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