Refactor MCP tool and server to handle optional server_context parameter

- Updated `call` method in `MCP::Tool` and `MCP::Prompt` to accept `server_context` as an optional parameter.
- Refactored `MCP::Server` to streamline argument handling for tool and prompt calls, introducing helper methods `call_tool_with_args` and `call_prompt_template_with_args`.
- Adjusted tests to reflect changes in method signatures and ensure compatibility with optional `server_context` parameter.

test/mcp/tool_test.rb

@@ -226,5 +226,40 @@ module MCP
       assert_equal response.content, [{ type: "text", content: "OK" }]
       assert_equal response.is_error, false
     end
+
+    class TestToolWithoutServerContext < Tool
+      tool_name "test_tool_without_server_context"
+      description "a test tool for testing without server context"
+      input_schema({ properties: { message: { type: "string" } }, required: ["message"] })
+
+      class << self
+        def call(message:)
+          Tool::Response.new([{ type: "text", content: "OK" }])
+        end
+      end
+    end
+
+    class TestToolWithoutRequired < Tool
+      tool_name "test_tool_without_required"
+      description "a test tool for testing without required server context"
+
+      class << self
+        def call(message, server_context: nil)
+          Tool::Response.new([{ type: "text", content: "OK" }])
+        end
+      end
+    end
+
+    test "tool call without server context" do
+      tool = TestToolWithoutServerContext
+      response = tool.call(message: "test")
+      assert_equal response.content, [{ type: "text", content: "OK" }]
+    end
+
+    test "tool call with server context and without required" do
+      tool = TestToolWithoutRequired
+      response = tool.call("test", server_context: { foo: "bar" })
+      assert_equal response.content, [{ type: "text", content: "OK" }]
+    end
   end
 end