Add logging to indicate when google play integrity is not available

[jleach]

If Google Play integrity is not available on device log a message indicating this fact.

    const available = await isPlayIntegrityAvailable()
    if (!available) {
      return null
    }

For a stretch goal, all logging should make it easier to search through by including a key word like:

log.error(`${componentName}: Google Play Integrity is unavailable`)

Prints

AttestationService: Google Play integrity is unavailable

[cvarjao]

This seems to be important enough that should surface some sort of error message as opposed to silently fails, no?