Android: Backend disk storage and integration tests

[getvictor]

• Populate the disk storage and % full
• Integration tests (at server/service or android/service level as appropriate)

Marko's notes on device storage

AMAPI returns memoryInfo which has totalRam and totalInternalStorage fields. Internal storage is not built-in storage, but storage that’s reserved to OS and some apps (see more in this post, or this one).

Additionally, AMAPI returns memoryEvents array which consists of measured values of disk space. EXTERNAL_STORAGE_DETECTED is actually not just external storage like an SD card but also built-in storage that is not internal storage mentioned in the paragraph above.

[marko-lisica]

@georgekarrv We have a story for this: #26822