fix(prost-build): Map wrapper types to primitives

[jen20]

Motivation

This commit address the issue raised in #2388, where well-known types such as google.protobuf.BoolValue would appear as super::bool rather than the correct primitives.

The issue was reproduced here, and produces the following output when cargo build is run (only the first occurrence is shown):

error[E0412]: cannot find type `bool` in module `super`
  --> /Users/James/Code/personal/tonic-repros/tonic-2388/target/debug/build/tonic-2388-685c45971c3ed332/out/helloworld.rs:95:53
   |
95 |             request: impl tonic::IntoRequest<super::bool>,
   |                                                     ^^^^ not found in `super`
   |
help: consider importing this builtin type
   |
11 +     use std::primitive::bool;
   |
help: if you import `bool`, refer to it directly
   |
95 -             request: impl tonic::IntoRequest<super::bool>,
95 +             request: impl tonic::IntoRequest<bool>,
   |

Solution

We address this by adding new cases to the existing enum for the various wrapper types contained in google/protobuf/wrappers.proto, when not compiling well-known types as proto structs directly. This is broadly in line with the patch suggested in the issue by @zhaohaiyun9, but is a little less broad and adds test coverage.