Simplify proto conversion

Trait based infra in conv.rs is significantly more complicated than
what we actually need here.

crates/rust-analyzer/src/lib.rs

@@ -20,9 +20,11 @@ macro_rules! eprintln {
 mod vfs_glob;
 mod caps;
 mod cargo_target_spec;
-mod conv;
+mod to_proto;
+mod from_proto;
 mod main_loop;
 mod markdown;
+// TODO: rename to lsp_ext
 pub mod req;
 pub mod config;
 mod world;