Request Document: go/android-rust-importing-crates
For CL Reviewers: go/android3p#cl-review
For Build Team: go/ab-third-party-imports

Bug: http://b/339172934
Test: m libhttp_body && atest --host http-body_test_src_lib http-body_test_tests_is_end_stream
Change-Id: I9c7b37b81983fa814a96b2f17276cf478486a6cf