Address pre-existing StrictMode violations

[fractalwrench]

Goal

Addresses some pre-existing StrictMode violations by moving affected code onto background threads where possible, and only calling Future#get() when the result is absolutely required.

Changeset

• Altered various storage setup methods to avoid unnecessary calls (e.g. DeviceIdStore no longer calls file.exists() as file.createNewFile() is sufficient)
• Altered ImmutableConfig so that persistenceDirectory is a lazy property. This avoids calling context#getCacheDir() on the main thread
• Simplified the Client constructor by extracting the construction and configuration of objects into related DependencyModules which form a dependency graph. These make it simpler to run I/O on background threads and also lay the framework for greater dependency injection in future.
• Altered device.freeDisk calculation to run on IO thread
• Set a traffic stats tag on network requests
• Loaded plugins on a background thread

Testing

Relied on existing test coverage. Confirmed the strictmode violations are resolved by enabling all penalties in the example app.

[bugsnagbot]

Android notifier sizes

Format	Size impact of Bugsnag (kB)	Size impact of Bugsnag when Minified (kB)
APK	1519.47	1409.46
arm64_v8a	410.3	299.71
armeabi	389.81	279.22
armeabi_v7a	373.44	262.85
x86	447.14	336.55
x86_64	430.77	320.18

Generated by 🚫 Danger

[lemnik]

LGTM