patch 8.2.4861: it is not easy to restore saved mappings

Problem:    It is not easy to restore saved mappings.
Solution:   Make mapset() accept a dict argument. (Ernie Rael, closes #10295)
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index e15993d..7b64fc4 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -2463,7 +2463,8 @@
         sid: SID(),
         scriptversion: 999999,
         rhs: 'bar',
-        buffer: 0})
+        buffer: 0,
+        abbr: 0})
   unmap foo
   v9.CheckDefAndScriptFailure(['maparg(1)'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1174: String required for argument 1'])
   v9.CheckDefAndScriptFailure(['maparg("a", 2)'], ['E1013: Argument 2: type mismatch, expected string but got number', 'E1174: String required for argument 2'])
@@ -2545,7 +2546,7 @@
 enddef
 
 def Test_mapset()
-  v9.CheckDefAndScriptFailure(['mapset(1, true, {})'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1174: String required for argument 1'])
+  v9.CheckDefAndScriptFailure(['mapset(1, true, {})'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1223: String or Dictionary required for argument 1'])
   v9.CheckDefAndScriptFailure(['mapset("a", 2, {})'], ['E1013: Argument 2: type mismatch, expected bool but got number', 'E1212: Bool required for argument 2'])
   v9.CheckDefAndScriptFailure(['mapset("a", false, [])'], ['E1013: Argument 3: type mismatch, expected dict<any> but got list<unknown>', 'E1206: Dictionary required for argument 3'])
 enddef