Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #2808

Job	Run time
checks / pre-commit	35s
checks / readme-snippets	10s
checks / test (3.11, lowest-direct, ubuntu-latest)	35s
checks / test (3.10, highest, ubuntu-latest)	35s
checks / test (3.10, highest, windows-latest)	2m 31s
checks / test (3.12, lowest-direct, windows-latest)	1m 44s
checks / test (3.11, lowest-direct, windows-latest)	1m 29s
checks / test (3.11, highest, ubuntu-latest)	34s
checks / test (3.12, lowest-direct, ubuntu-latest)	49s
checks / test (3.10, lowest-direct, windows-latest)	1m 33s
checks / test (3.11, highest, windows-latest)	1m 26s
checks / test (3.12, highest, ubuntu-latest)	34s
checks / test (3.10, lowest-direct, ubuntu-latest)	35s
checks / test (3.13, highest, windows-latest)	1m 19s
checks / test (3.13, highest, ubuntu-latest)	36s
checks / test (3.12, highest, windows-latest)	1m 27s
checks / test (3.13, lowest-direct, windows-latest)	1m 21s
checks / test (3.13, lowest-direct, ubuntu-latest)	34s
	18m 27s

Provide feedback