fix(tree): reassign fullpath when register new node which the same current node (#2366)

* fix(tree): assign fullpath to current node by fullpath of new node if current node the same new node

* test(router-test): reverse the order when register router when test func GetFullPath

* chg(tree-test): update test case with register new route in TestRouteContextHoldsFullPath

Co-authored-by: vinhha <vinhha@vng.com.vn>
Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>

tree.go

@@ -240,6 +240,7 @@ walk:
 			panic("handlers are already registered for path '" + fullPath + "'")
 		}
 		n.handlers = handlers
+		n.fullPath = fullPath
 		return
 	}
 }