feat(nvim_open_term): convert LF => CRLF (#26384)

Problem:
Unlike termopen(), nvim_open_term() PTYs do not carriage-return the
cursor on newline ("\n") input.

    nvim --clean
    :let chan_id = nvim_open_term(1, {})
    :call chansend(chan_id, ["here", "are", "some", "lines"])

Actual behavior:

    here
        are
           some
               lines

Expected behaviour:

    here
    are
    some
    lines

Solution:
Add `force_crlf` option, and enable it by default.

src/nvim/terminal.h

@@ -16,6 +16,7 @@ typedef struct {
   terminal_write_cb write_cb;
   terminal_resize_cb resize_cb;
   terminal_close_cb close_cb;
+  bool force_crlf;
 } TerminalOptions;
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS