Multi-arch Play Store builds

[ximenabb]

Description :
Currently if someone downloads Mapeo Mobile from the Google Play store they will receive the APK that is only for their phone's architecture (e.g. only Arm v7 or Arm64). This means that they can only update devices that are the same architecture.

If we change the Play Store upload to be a multi-arch build (with both Arm v7 and Arm64) then it will increase the download size (~40 MB -> ~65 MB) but they will then be able to share the update with most other phones.

There are some very rare Intel (x86) phones, but too rare (<1% and not since 2015) to justify another doubling of download size. Intel devices will need to update from each other or use the internet.

Acceptance Criteria :
Have done a test publish of a forked version of Mapeo to the Play store and tested it installs a multi-arch APK on a test device.

Technical Notes:
Notes added by the tech team - TO ADD

Points:

[ximenabb]

kira's proposal : merge and do a no change point release