{.deprecated: [existsFile: fileExists].} (#14735)

* {.deprecated: [existsFile: fileExists].}

* s/existsFile/fileExists/ except under deps

* workaround pending #14819

* fix test

tests/manyloc/keineschweine/enet_server/enet_server.nim

@@ -118,7 +118,7 @@ when true:
       of cmdShortOption, cmdLongOption:
         case key
         of "f", "file":
-          if existsFile(val):
+          if fileExists(val):
             zoneCfgFile = val
           else:
             echo("File does not exist: ", val)
@@ -136,7 +136,7 @@ when true:
     address.port = port
 
     var path = getAppDir()/../"data"/zoneFile
-    if not existsFile(path):
+    if not fileExists(path):
       echo("Zone settings file does not exist: ../data/", zoneFile)
       echo(path)
       quit(1)