fix: fill missing fully qualified syntax in prompt_handler macros (#866)

* fix: fill missing fully qualified syntax in prompt_handler macros

* fix: remove unused prompt handler test imports

---------

Co-authored-by: Dale Seo <5466341+DaleSeo@users.noreply.github.com>

crates/rmcp/tests/test_prompt_handler.rs

@@ -3,13 +3,7 @@
 // the ServerHandler trait implementation methods.
 #![allow(dead_code)]
 
-use rmcp::{
-    RoleServer, ServerHandler,
-    handler::server::router::prompt::PromptRouter,
-    model::{GetPromptRequestParams, GetPromptResult, ListPromptsResult, PaginatedRequestParams},
-    prompt_handler,
-    service::RequestContext,
-};
+use rmcp::{ServerHandler, handler::server::router::prompt::PromptRouter, prompt_handler};
 
 #[derive(Debug, Clone)]
 pub struct TestPromptServer {