vim-patch:partial:9.0.0719: too many delete() calls in tests

Problem:    Too many delete() calls in tests.
Solution:   Use deferred delete where possible.

56564964e6

This includes all changes expect changes in test_startup.vim.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

test/old/testdir/test_syntax.vim

@@ -644,15 +644,16 @@ func Test_syntax_c()
 	\ '   printf("Just an example piece of C code\n");',
 	\ '   return 0x0ff;',
 	\ '}',
+	\ "\t\t ",
 	\ '   static void',
 	\ 'myFunction(const double count, struct nothing, long there) {',
-	\ '  // 123: nothing to read here',
-	\ '  for (int i = 0; i < count; ++i) {',
-	\ '    break;',
-	\ '  }',
-	\ "  Note: asdf",
+	\ "\t// 123: nothing to endif here",
+	\ "\tfor (int i = 0; i < count; ++i) {",
+	\ "\t   break;",
+	\ "\t}",
+	\ "\tNote: asdf",
 	\ '}',
-	\ ], 'Xtest.c')
+	\ ], 'Xtest.c', 'D')
 
   " This makes the default for 'background' use "dark", check that the
   " response to t_RB corrects it to "light".
@@ -664,7 +665,6 @@ func Test_syntax_c()
   call StopVimInTerminal(buf)
 
   let $COLORFGBG = ''
-  call delete('Xtest.c')
 endfun
 
 " Test \z(...) along with \z1
@@ -698,10 +698,10 @@ func Test_syn_wrong_z_one()
 endfunc
 
 func Test_syntax_after_bufdo()
-  call writefile(['/* aaa comment */'], 'Xaaa.c')
-  call writefile(['/* bbb comment */'], 'Xbbb.c')
-  call writefile(['/* ccc comment */'], 'Xccc.c')
-  call writefile(['/* ddd comment */'], 'Xddd.c')
+  call writefile(['/* aaa comment */'], 'Xaaa.c', 'D')
+  call writefile(['/* bbb comment */'], 'Xbbb.c', 'D')
+  call writefile(['/* ccc comment */'], 'Xccc.c', 'D')
+  call writefile(['/* ddd comment */'], 'Xddd.c', 'D')
 
   let bnr = bufnr('%')
   new Xaaa.c
@@ -729,10 +729,6 @@ func Test_syntax_after_bufdo()
   bwipe! Xccc.c
   bwipe! Xddd.c
   syntax off
-  call delete('Xaaa.c')
-  call delete('Xbbb.c')
-  call delete('Xccc.c')
-  call delete('Xddd.c')
 endfunc
 
 func Test_syntax_foldlevel()