Please add support for server compression

### Is your feature request related to a problem? Please describe.
Not really, other than the fact that I cannot migrate my server from `grpc` to `@grpc/grpc-js` until `@grpc/grpc-js` supports compression. Our clients (millions of them...) send messages compressed (gzip) in a bi-directional stream. Also, `@grpc/grpc-js` does not return an `UNIMPLEMENTED` error when the client sends the `grpc-compression` header with a value other than `identity`...

### Describe the solution you'd like
Something along the lines of what is implemented in https://www.npmjs.com/package/grpc-server-js (I just perused through that code and found out that they already support compression) It also looks like this has been partially implemented in `compression-filter.ts` already... And I see a lot of `TODO(cjihrig)` in the code to point to the areas that should be modified.

### Describe alternatives you've considered
Keep using the `grpc` package for now, even though it explicitly says that it has been deprecated. Compression is a major feature IMO, so maybe the deprecation was a little hasty?