patch 9.1.0329: String interpolation fails for Dict type

Problem:  String interpolation fails for Dict type
Solution: Support Dict data type properly, also support :put =Dict
          (without having to convert it to string() first)
          (Yegappan Lakshmanan)

fixes: #14529
closes: #14541

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_edit.vim b/src/testdir/test_edit.vim
index cdf2097..789e44c 100644
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -1962,8 +1962,8 @@
 
   let buf = RunVimInTerminal('', #{rows: 6, cols: 60})
 
-  " trying to insert a dictionary produces an error
-  call term_sendkeys(buf, "i\<C-R>={}\<CR>")
+  " trying to insert a blob produces an error
+  call term_sendkeys(buf, "i\<C-R>=0z\<CR>")
 
   " ending Insert mode should put the cursor back on the ':'
   call term_sendkeys(buf, ":\<Esc>")