paste/cmdline: discard all chunks after first line

Problem:  If multiple paste "chunks" are streamed, chunks after the
          first line are pasted into the buffer.
Solution: Check for cmdline-mode for all chunks in a paste-stream.

src/nvim/lua/vim.lua

@@ -191,10 +191,8 @@ paste = (function()
       local line1, _ = string.gsub(lines[1], '[\r\n\012\027]', ' ')  -- Scrub.
       vim.api.nvim_input(line1)
       vim.api.nvim_set_option('paste', false)
-    elseif mode == 'i' or mode == 'R' then
+    elseif mode ~= 'c' then
-      vim.api.nvim_put(lines, 'c', false, true)
+      vim.api.nvim_put(lines, 'c', (mode ~= 'i' and mode ~= 'R'), true)
-    else
-      vim.api.nvim_put(lines, 'c', true, true)
     end
     if phase ~= -1 and (now - tdots >= 100) then
       local dots = ('.'):rep(tick % 4)

test/functional/terminal/tui_spec.lua

@@ -363,7 +363,10 @@ describe('TUI', function()
     feed_data('\027[D')   -- <Left> to place cursor between quotes.
     wait_for_mode('c')
     -- "bracketed paste"
-    feed_data('\027[200~line 1\nline 2\n\027[201~')
+    feed_data('\027[200~line 1\nline 2\n')
+    wait_for_mode('c')
+    feed_data('line 3\nline 4\n\027[201~')
+    wait_for_mode('c')
     screen:expect{grid=[[
       foo                                               |
                                                         |
@@ -505,7 +508,7 @@ describe('TUI', function()
                                                         |
       {4:~                                                 }|
       {5:                                                  }|
-      {8:paste: Error executing lua: vim.lua:197: Vim:E21: }|
+      {8:paste: Error executing lua: vim.lua:195: Vim:E21: }|
       {8:Cannot make changes, 'modifiable' is off}          |
       {10:Press ENTER or type command to continue}{1: }          |
       {3:-- TERMINAL --}                                    |