Eventloop cleanup (#2577)

* eventloop: Use eventloop namespace in cpp files

* changelog: Add missing deprecated hook message

* Make eventloop and ipc classes non-copyable and non-movable

* Remove functional.hpp

* eventloop: Don't close handles in error cases

Client should be responsible for closing handles.

* eventloop: Address invalidation of handle references

include/utils/command.hpp

@@ -5,7 +5,6 @@
 #include "components/types.hpp"
 #include "errors.hpp"
 #include "utils/file.hpp"
-#include "utils/functional.hpp"
 
 POLYBAR_NS
 
@@ -86,7 +85,7 @@ class command<output_policy::REDIRECTED> : private command<output_policy::IGNORE
   using command<output_policy::IGNORED>::get_pid;
   using command<output_policy::IGNORED>::get_exit_status;
 
-  void tail(callback<string> cb);
+  void tail(std::function<void(string)> cb);
   string readline();
 
   int get_stdout(int c);