Remove unnecessary `alloc` feature guards in `roto-tonic`. Add
`roto-runtime` dependency to `codegen`, fix test data paths, and
include `async-trait` in the hello world build test.
Update imports to use `roto_tonic` instead of `crate` for BufferPool
and StatusBody. Remove the broad replacement of `crate` with `roto`
and add error output to `test_map_build.rs`.
Correct module paths and accessor usage in the generator to ensure
generated code builds. Add a test that verifies this by compiling the
generated code in a temporary project.
charles