community/libappindicator: upgrade to ubuntu 20.10 release, add --enable-introspection option
Required to build /usr/lib/girepository-1.0/AppIndicator3-0.1.typelib, which is used by blueman.
Also adds libappindicator to blueman depends and uses proper tests.
(FYI - libappindicator isn't detected as a dependency by scanelf because it's not called from a binary, but rather a Python script. Same with bluez, dbus and gtk+3.0.)