Make _client depend on the _transports package instead of its submodules

[hoodmane]

Split from #1022

[codspeed-hq]

Merging this PR will not alter performance

✅ 15 untouched benchmarks
⏩ 7 skipped benchmarks¹

---

_{Comparing hoodmane:fix-transports-import (b6dca55) with main (5d9eedc)}

Footnotes

1. 7 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}