paste: insert before cursor always

Inserting "after" the cursor in Normal-mode, for big paste-streams, is
not reliable: sometimes the text "after" the cursor ends up in the
middle of the pasted text.  Maybe the cursor position is not updated?

To avoid weird behavior, always paste "before".  Maybe nvim_put() or
vim.paste() can be fixed more properly later.

runtime/doc/provider.txt

@@ -239,7 +239,7 @@ GUIs can paste by calling |nvim_paste()|.
 
 PASTE BEHAVIOR ~
 
-Paste inserts text after the cursor.  Lines break at <NL>, <CR>, and <CR><NL>.
+Paste inserts text before the cursor.  Lines break at <NL>, <CR> and <CR><NL>.
 When pasting a huge amount of text, screen-updates are throttled and the
 message area shows a "..." pulse.
 

src/nvim/lua/vim.lua

@@ -192,7 +192,7 @@ paste = (function()
       vim.api.nvim_input(line1)
       vim.api.nvim_set_option('paste', false)
     elseif mode ~= 'c' then
-      vim.api.nvim_put(lines, 'c', (mode ~= 'i' and mode ~= 'R'), true)
+      vim.api.nvim_put(lines, 'c', false, true)
     end
     if phase ~= -1 and (now - tdots >= 100) then
       local dots = ('.'):rep(tick % 4)

test/functional/terminal/tui_spec.lua

@@ -485,9 +485,9 @@ describe('TUI', function()
     feed_data('\n')  -- <CR>
     screen:expect{grid=[[
       foo                                               |
-      typed input...line A                              |
+      typed input..line A                               |
       line B                                            |
-      {1: }                                                 |
+      {1:.}                                                 |
       {5:[No Name] [+]                                     }|
                                                         |
       {3:-- TERMINAL --}                                    |