patch 8.2.2638: cannot write a message to the terminal from the GUI

Problem:    Cannot write a message to the terminal from the GUI.
Solution:   Add :echoconsole and use it in the test runner. (issue #7975)

src/testdir/runtest.vim

@@ -162,7 +162,7 @@ function GetAllocId(name)
 endfunc
 
 func RunTheTest(test)
-  echo 'Executing ' . a:test
+  echoconsole 'Executing ' . a:test
   if has('reltime')
     let func_start = reltime()
   endif