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>

Start by reproducing the mapping behavior with the two nnoremap commands from the issue, then read the XTerm modifyOtherKeys documentation and compare it with MacVim's keyboard input handling. The work is done when and , along with analogous control-key pairs, can trigger separate mappings and the example commands report distinct messages.