replace XUL <textbox> with <html:input>

Mozilla has removed XUL , although only partially in the ESR68 timeframe (see legacy/trac#32154 (moved) where we had to replace a multiline usage with html:textarea). We need to finish the job and replace our remaining uses of with html:input.

While we are at it, we should double check that we do not use outside of Tor Launcher, either in the Torbutton code or in a Firefox patch.