feat(terminal)!: include cursor position in TermRequest event data (#31609)

When a plugin registers a TermRequest handler there is currently no way
for the handler to know where the terminal's cursor position was when
the sequence was received. This is often useful information, e.g. for
OSC 133 sequences which are used to annotate shell prompts.

Modify the event data for the TermRequest autocommand to be a table
instead of just a string. The "sequence" field of the table contains the
sequence string and the "cursor" field contains the cursor
position when the sequence was received.

To maintain consistency between TermRequest and TermResponse (and to
future proof the latter), TermResponse's event data is also updated to
be a table with a "sequence" field.

BREAKING CHANGE: event data for TermRequest and TermResponse is now a
table

test/functional/terminal/buffer_spec.lua

@@ -373,7 +373,7 @@ describe(':terminal buffer', function()
       })
       vim.api.nvim_create_autocmd('TermRequest', {
         callback = function(args)
-          if args.data == '\027]11;?' then
+          if args.data.sequence == '\027]11;?' then
             table.insert(_G.input, '\027]11;rgb:0000/0000/0000\027\\')
           end
         end
@@ -389,6 +389,42 @@ describe(':terminal buffer', function()
     }, exec_lua('return _G.input'))
   end)
 
+  it('TermRequest includes cursor position #31609', function()
+    command('autocmd! nvim.terminal TermRequest')
+    local screen = Screen.new(50, 10)
+    local term = exec_lua([[
+      _G.cursor = {}
+      local term = vim.api.nvim_open_term(0, {})
+      vim.api.nvim_create_autocmd('TermRequest', {
+        callback = function(args)
+          _G.cursor = args.data.cursor
+        end
+      })
+      return term
+    ]])
+    -- Enter terminal mode so that the cursor follows the output
+    feed('a')
+
+    -- Put some lines into the scrollback. This tests the conversion from terminal line to buffer
+    -- line.
+    api.nvim_chan_send(term, string.rep('>\n', 20))
+    screen:expect([[
+      >                                                 |*8
+      ^                                                  |
+      {5:-- TERMINAL --}                                    |
+    ]])
+
+    -- Emit an OSC escape sequence
+    api.nvim_chan_send(term, 'Hello\nworld!\027]133;D\027\\')
+    screen:expect([[
+      >                                                 |*7
+      Hello                                             |
+      world!^                                            |
+      {5:-- TERMINAL --}                                    |
+    ]])
+    eq({ 22, 6 }, exec_lua('return _G.cursor'))
+  end)
+
   it('no heap-buffer-overflow when using jobstart("echo",{term=true}) #3161', function()
     local testfilename = 'Xtestfile-functional-terminal-buffers_spec'
     write_file(testfilename, 'aaaaaaaaaaaaaaaaaaaaaaaaaaaa')