[Rust Server] Generate valid Rustdocs for lazy_static items

Created by: richardwhiuk

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  • @frol, @farcaller, @bjgill

Description of the PR

Generate valid Rustdocs for lazy_static items

Currently compiling a generated crate produced by rust-server produces warnings such as the follows:

warning: unused doc comment
  --> output/rust-server-test/src/mimetypes.rs:15:5
   |
15 |       /// Create Mime objects for the response content types for RawJsonGet
   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
16 | /     lazy_static! {
17 | |         pub static ref RAW_JSON_GET_SUCCESS: Mime = "*/*".parse().unwrap();
18 | |     }
   | |_____- rustdoc does not generate documentation for macro expansions
   |
   = help: to document an item produced by a macro, the macro must produce the documentation as part of its expansion

This fixes that. This work was contributed by @mthebridge