Removing unused tests/timeloop.c and tests/timeloop-basic.c

Remove unused tests/timelooop.c and tests/timeloop-basic.c because
these programs are manual performance tests which are no more relevant
for glib. They were used for the writing of GMainLoop but since then
they haven't not much been used in 22 years, it is safe to remove them.

Helps issue #1434

tests/meson.build

@@ -45,11 +45,7 @@ test_extra_programs = {
   'assert-msg-test' : {},
 }
 
-if host_machine.system() != 'windows'
-  tests += {
-    'timeloop' : {},
-  }
-else
+if host_machine.system() == 'windows'
   test_extra_programs += {
     'spawn-test-win32-gui' : {'gui_app' : true}
   }