patch 8.2.2435: setline() gives an error for some types

Problem:    setline() gives an error for some types.
Solution:   Allow any type, convert each item to a string.
diff --git a/src/testdir/test_bufline.vim b/src/testdir/test_bufline.vim
index 0f5bac8..b2de198 100644
--- a/src/testdir/test_bufline.vim
+++ b/src/testdir/test_bufline.vim
@@ -5,6 +5,7 @@
 source check.vim
 
 func Test_setbufline_getbufline()
+  " similar to Test_set_get_bufline()
   new
   let b = bufnr('%')
   hide
@@ -38,6 +39,12 @@
   call assert_equal(['e'], getbufline(b, 5))
   call assert_equal([], getbufline(b, 6))
   call assert_equal([], getbufline(b, 2, 1))
+
+  call setbufline(b, 2, [function('eval'), #{key: 123}, test_null_job()])
+  call assert_equal(["function('eval')",
+                  \ "{'key': 123}",
+                  \ "no process"],
+                  \ getbufline(b, 2, 4))
   exe "bwipe! " . b
 endfunc