"nvim -es": disable shada #21723

Problem:
`nvim -es` (and `nvim -Es`) is the recommended way to non-interactively
run commands/vimscript. But it enables shada by default, which is
usually not wanted.

Solution:
- Disable shada by default for `nvim -es/-Es`. This can be overridden by
  `-i foo` if needed.
- Do NOT change the 'loadplugins' default.
  - User config + packages _should_ be enabled by default, for both `nvim
    -es` and `nvim -l`. Else any Lua packages you have can't be accessed
    without `-u path/to/config`, which is clumsy.
      - Use-cases:
        ```
        nvim --headless "+Lazy! sync" +qa
            would become: nvim -es "+Lazy! sync"
        nvim --headless +PlugInstall +qall
            would become: nvim -es +PlugInstall
        ```
  - Opt-out (`--clean` or `-u NONE`) is much easier than opt-in (`-u
    path/to/config`).
  -  User config/packages are analogous to pip packages, which are
     expected when doing `python -c ...`.

related: 7c94bcd2d7
related: ddd0eb6f51

src/nvim/message.c

@@ -2719,7 +2719,7 @@ static msgchunk_T *disp_sb_line(int row, msgchunk_T *smp)
 }
 
 /// @return  true when messages should be printed to stdout/stderr:
-///          - "batch mode" ("silent mode", -es/-Es)
+///          - "batch mode" ("silent mode", -es/-Es/-l)
 ///          - no UI and not embedded
 int msg_use_printf(void)
 {