vim-patch:8.2.2643: various code not covered by tests

Problem:    Various code not covered by tests.
Solution:   Add a few more test. (Yegappan Lakshmanan, closes vim/vim#7995)
1f448d906b

Cherry-pick some test_edit.vim changes from patches 8.2.{1022,1432}.
Reorder test_undo.vim to match upstream.

test/functional/legacy/edit_spec.lua

@@ -0,0 +1,26 @@
+local helpers = require('test.functional.helpers')(after_each)
+local clear = helpers.clear
+local command = helpers.command
+local expect = helpers.expect
+local feed = helpers.feed
+local sleep = helpers.sleep
+
+before_each(clear)
+
+-- oldtest: Test_autoindent_remove_indent()
+it('autoindent removes indent when Insert mode is stopped', function()
+  command('set autoindent')
+  -- leaving insert mode in a new line with indent added by autoindent, should
+  -- remove the indent.
+  feed('i<Tab>foo<CR><Esc>')
+  -- Need to delay for sometime, otherwise the code in getchar.c will not be
+  -- exercised.
+  sleep(50)
+  -- when a line is wrapped and the cursor is at the start of the second line,
+  -- leaving insert mode, should move the cursor back to the first line.
+  feed('o' .. ('x'):rep(20) .. '<Esc>')
+  -- Need to delay for sometime, otherwise the code in getchar.c will not be
+  -- exercised.
+  sleep(50)
+  expect('\tfoo\n\n' .. ('x'):rep(20))
+end)