Add ability to map <TAB> and <C-I> separately like XTerm or iTerm2 have done

Is your feature request about something that is currently impossible or hard to do? Please describe the problem.
Currently we can't remap for example <TAB> and <C-I> separately, they both always do the same thing.

Describe the solution you'd like
Would be nice if these, and other control keys (<CR> and <C-M>, <BS> and <C-H> etc.), could be mapped separately.

Additional context
<TAB> and <C-I> can already be mapped separately in a Vim 8.2 running XTerm using modifyOtherKeys https://invisible-island.net/xterm/modified-keys.html or in iTerm2 when 'Control sequences can enable modifyOtherKeys mode' has been enabled from Preferences -> Profiles -> Keys.

One can easily test if the keys get registered separately with:

nnoremap <C-I> :echom "Ctrl-I was pressed"<CR>
nnoremap <TAB> :echom "Tab was pressed"<CR>

首先使用 issue 中的两个 nnoremap 命令复现映射行为，然后阅读 XTerm modifyOtherKeys 文档，并将其与 MacVim 的键盘输入处理进行比较。当 和 以及类似的控制键对能够触发不同的映射，并且示例命令报告不同的消息时，工作即告完成。