Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #3075

Job	Run time
checks / pre-commit	30s
checks / readme-snippets	13s
checks / test (3.10, highest, ubuntu-latest)	38s
checks / test (3.11, lowest-direct, ubuntu-latest)	36s
checks / test (3.10, highest, windows-latest)	1m 27s
checks / test (3.11, lowest-direct, windows-latest)	1m 37s
checks / test (3.11, highest, ubuntu-latest)	33s
checks / test (3.12, lowest-direct, ubuntu-latest)	38s
checks / test (3.12, highest, ubuntu-latest)	33s
checks / test (3.10, lowest-direct, ubuntu-latest)	38s
checks / test (3.10, lowest-direct, windows-latest)	1m 27s
checks / test (3.13, lowest-direct, windows-latest)	1m 32s
checks / test (3.13, highest, ubuntu-latest)	33s
checks / test (3.13, lowest-direct, ubuntu-latest)	37s
checks / test (3.11, highest, windows-latest)	1m 34s
checks / test (3.13, highest, windows-latest)	1m 23s
checks / test (3.12, highest, windows-latest)	1m 22s
checks / test (3.12, lowest-direct, windows-latest)	1m 44s
	17m 35s

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