Introduce support for new VM based minicap to support Android 12

This commit introduce a new option to use a new minicap
implementation by specifying --screen-grabber or the env
variable SCREEN_GRABBER. The current native minicap is the default
and is refered as 'minicap-bin'. The new minicap which is packaged
in an apk is usable with 'minicap-apk' and will be used as a
fallback.
At the moment, this apk is expected to be included in
minicap-prebuilt node package at this location
minicap-prebuilt/prebuilt/noarch/minicap.apk.

STFService.apk has also been updated to take into account Android 12

Signed-off-by: Crepieux Pierre <pierre.crepieux@orange.com>

lib/units/device/plugins/screen/capture.js

@@ -33,7 +33,7 @@ module.exports = syrup.serial()
       log.info('Capturing screenshot')
 
       var file = util.format('/data/local/tmp/minicap_%d.jpg', Date.now())
-      return minicap.run(util.format(
+      return minicap.run('minicap-apk', util.format(
           '-P %s -s >%s', projectionFormat(), file))
         .then(adbkit.util.readAll)
         .then(function() {