refactor(tui): use nvim_echo() for verbose terminfo

This is needed for #18375 for the obvious reasons.
note: verbose_terminfo_event is only temporarily needed
until the full TUI process refactor is merged.

test/functional/ui/options_spec.lua

@@ -24,6 +24,7 @@ describe('UI receives option updates', function()
       termguicolors=false,
       ttimeout=true,
       ttimeoutlen=50,
+      verbose=0,
       ext_cmdline=false,
       ext_popupmenu=false,
       ext_tabline=false,