Google Play Billing v5 migration

[mmathieum]

Tasks:

• [x] migrate
• [x] test local dev release build
• [x] test Play Store release build

Links:

• https://developer.android.com/google/play/billing/migrate-gpblv5

[mmathieum]

https://github.com/mtransitapps/commons-android/commit/2df9c3f1367f9e152082ae17be5cbf6e14452193

https://github.com/mtransitapps/mtransit-for-android/commit/4ec74f1db8c8c2282c441eabd5ce15d5ebe4991d https://github.com/mtransitapps/mtransit-for-android/commit/879a8d2e25ef721bbfe7e1c3cefa5b602860f132

https://github.com/mtransitapps/mtransit-for-android-gradle/commit/91d76f95fa4a3a94afe4b6e1e6bac163a14c7ab2 https://github.com/mtransitapps/mtransit-for-android-gradle/commit/95f4a40b960aeb50dd032e58d76157c60d31a431