Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #3401

Job	Run time
checks / pre-commit	32s
checks / readme-snippets	10s
checks / test (3.10, lowest-direct, ubuntu-latest)	43s
checks / test (3.10, lowest-direct, windows-latest)	2m 39s
checks / test (3.11, lowest-direct, ubuntu-latest)	44s
checks / test (3.11, highest, ubuntu-latest)	43s
checks / test (3.10, highest, windows-latest)	1m 55s
checks / test (3.11, highest, windows-latest)	2m 55s
checks / test (3.11, lowest-direct, windows-latest)	2m 25s
checks / test (3.12, highest, ubuntu-latest)	48s
checks / test (3.10, highest, ubuntu-latest)	43s
checks / test (3.13, lowest-direct, ubuntu-latest)	43s
checks / test (3.12, lowest-direct, ubuntu-latest)	45s
checks / test (3.12, lowest-direct, windows-latest)	3m 10s
checks / test (3.13, highest, windows-latest)	2m 3s
checks / test (3.13, highest, ubuntu-latest)	40s
checks / test (3.13, lowest-direct, windows-latest)	2m 23s
checks / test (3.12, highest, windows-latest)	2m 58s
	26m 59s

Provide feedback