fix(volo-build): escape keywords in code generation for idl service method arguments

[Ggiggle]

Motivation

To solve the #495 when a argument name in an IDL service method conflicts with a Rust syntax keyword, which results in a compilation error in the generated code.

service HelloService {
    HelloResponse Hello1 (1: HelloRequest type)
    HelloResponse Hello2 (1: HelloRequest self)
}

Solution

In the above example, type is a keyword in rust, so we will generate this field name as r#type in code. And when you use volo cli tool to initialize your project, this field name will be generated as _type in the server code template, so you should rename it as r#type when using it. In the two scenes, keyword like self will be generated as _self.