Include release train in tag produced by signtag
Currently signtag outputs a tag as tbb-[% c("var/torbrowser_version") %]-[% c("var/torbrowser_build") %] (such as tbb-10.0.3-build1). Unfortunately, now we must tag two different branches for the same Tor Browser version number (desktop and Android). We could begin by including desktop and android in the tagname, such as tbb-10.0.4-desktop-build1 and tbb-10.0.4-android-build1, or we can use esr and rr (or something else similar) for indicating the ESR train or Rapid Release train because we will slowly move other platforms onto rapid release in the future. This results in tbb-10.0.4-esr-build1 and tbb-10.0.4-rr-build1.