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>

Beginne damit, das Mapping-Verhalten mit den beiden nnoremap-Befehlen aus dem Issue zu reproduzieren. Lies dann die Dokumentation zu XTerm modifyOtherKeys und vergleiche sie mit MacVims Verarbeitung von Tastatureingaben. Die Arbeit ist abgeschlossen, wenn und sowie analoge Steuerungs-Tastenpaare separate Mappings auslösen können und die Beispielbefehle unterschiedliche Meldungen ausgeben.