patch 9.0.0336: tests are flaky because of using a common file name

Problem:    Tests are flaky because of using a common file name.
Solution:   Rename files and directories to be more unique.
diff --git a/src/testdir/test_edit.vim b/src/testdir/test_edit.vim
index a568fb2..a2d2b5e 100644
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -424,7 +424,7 @@
 " terminal.
 func Test_autoindent_remove_indent()
   CheckRunVimInTerminal
-  let buf = RunVimInTerminal('-N Xfile', {'rows': 6, 'cols' : 20})
+  let buf = RunVimInTerminal('-N Xarifile', {'rows': 6, 'cols' : 20})
   call TermWait(buf)
   call term_sendkeys(buf, ":set autoindent\n")
   " leaving insert mode in a new line with indent added by autoindent, should
@@ -442,8 +442,8 @@
   call term_sendkeys(buf, ":w\n")
   call TermWait(buf)
   call StopVimInTerminal(buf)
-  call assert_equal(["\tfoo", '', repeat('x', 20)], readfile('Xfile'))
-  call delete('Xfile')
+  call assert_equal(["\tfoo", '', repeat('x', 20)], readfile('Xarifile'))
+  call delete('Xarifile')
 endfunc
 
 func Test_edit_CR()
@@ -1530,7 +1530,7 @@
   let longfilename = longdirname . '/' . repeat('a', 255)
   call writefile(['Totum', 'Table'], longfilename)
   new
-  exe "next Xfile " . longfilename
+  exe "next Xnofile " . longfilename
   exe "normal iT\<C-N>"
 
   bwipe!
@@ -1754,19 +1754,19 @@
 " Test for editing a file using invalid file encoding
 func Test_edit_invalid_encoding()
   CheckEnglish
-  call writefile([], 'Xfile')
+  call writefile([], 'Xinvfile')
   redir => msg
-  new ++enc=axbyc Xfile
+  new ++enc=axbyc Xinvfile
   redir END
   call assert_match('\[NOT converted\]', msg)
-  call delete('Xfile')
+  call delete('Xinvfile')
   close!
 endfunc
 
 " Test for the "charconvert" option
 func Test_edit_charconvert()
   CheckEnglish
-  call writefile(['one', 'two'], 'Xfile')
+  call writefile(['one', 'two'], 'Xccfile')
 
   " set 'charconvert' to a non-existing function
   set charconvert=NonExitingFunc()
@@ -1774,7 +1774,7 @@
   let caught_e117 = v:false
   try
     redir => msg
-    edit ++enc=axbyc Xfile
+    edit ++enc=axbyc Xccfile
   catch /E117:/
     let caught_e117 = v:true
   finally
@@ -1792,7 +1792,7 @@
   set charconvert=Cconv1()
   new
   redir => msg
-  edit ++enc=axbyc Xfile
+  edit ++enc=axbyc Xccfile
   redir END
   call assert_equal(['one', 'two'], getline(1, '$'))
   call assert_match("can't read output of 'charconvert'", msg)
@@ -1807,10 +1807,10 @@
     call writefile(data, v:fname_out)
   endfunc
   set charconvert=Cconv2()
-  new Xfile
-  write ++enc=ucase Xfile1
-  call assert_equal(['ONE', 'TWO'], readfile('Xfile1'))
-  call delete('Xfile1')
+  new Xccfile
+  write ++enc=ucase Xccfile1
+  call assert_equal(['ONE', 'TWO'], readfile('Xccfile1'))
+  call delete('Xccfile1')
   close!
   delfunc Cconv2
   set charconvert&
@@ -1821,13 +1821,13 @@
   endfunc
   set charconvert=Cconv3()
   new
-  call assert_fails('edit ++enc=lcase Xfile', 'E202:')
+  call assert_fails('edit ++enc=lcase Xccfile', 'E202:')
   call assert_equal([''], getline(1, '$'))
   close!
   delfunc Cconv3
   set charconvert&
 
-  call delete('Xfile')
+  call delete('Xccfile')
 endfunc
 
 " Test for editing a file without read permission
@@ -1835,17 +1835,17 @@
   CheckUnix
   CheckNotRoot
 
-  call writefile(['one', 'two'], 'Xfile')
-  call setfperm('Xfile', '-w-------')
+  call writefile(['one', 'two'], 'Xnrpfile')
+  call setfperm('Xnrpfile', '-w-------')
   new
   redir => msg
-  edit Xfile
+  edit Xnrpfile
   redir END
   call assert_equal(1, &readonly)
   call assert_equal([''], getline(1, '$'))
   call assert_match('\[Permission Denied\]', msg)
   close!
-  call delete('Xfile')
+  call delete('Xnrpfile')
 endfunc
 
 " Using :edit without leaving 'insertmode' should not cause Insert mode to be