Some changes I would make to gRPC, if I needn't worry about backwards compatibility.

• Status should not have the static members for each Code.
• Status factory constructors should have required a String for the reason, rather than leaving it optional. It's too easy to forget.
• StatusRuntimeException and StatusException should have been named StatusException and StatusCheckedException. The SRE version is too long, and by far the more common.
• Same with Status.asRuntimeException(). It's common enough that it deserves a shortname.