Import macro directly rather than using #[macro_use].

`extern crate` makes it harder to keep track of dependencies, so we
prefer to import macros explicitly instead.

Bug: 261037227
Test: m example_service_fuzzer parcel_fuzzer_rs
Test: atest libbinder_rs-internal_test libbinder_ndk_bindgen_test
Change-Id: I6dbce8ee985d0a850ddddf8d08d5b330f5f13c9f