Update Android interview notes: modernize APIs, deprecations, and fill missing topics

[Senchick]

Motivation

• Bring the Android interview notes up-to-date with modern platform behavior, API deprecations and recommended replacements.
• Clarify lifecycle/startup ordering, background execution and storage/security best practices that changed in recent Android releases.
• Preserve mentions of older APIs (mark as deprecated/"устаревшее, но иногда спрашивают") when they remain relevant for interviews.
• Fill gaps for common interview topics (DataStore, WorkManager, Image handling, notifications, ART internals, memory/battery tools).

Description

• Updated section/android.md with precise technical clarifications such as Context being an abstract class, Application vs ContentProvider startup ordering, and that process entry is ActivityThread.main() after Zygote forks.
• Added modern guidance and deprecation context: onActivityCreated and setRetainInstance marked deprecated, recommend ViewModel/SavedStateHandle, prefer ViewPager2/FragmentStateAdapter over legacy adapters, and note IntentService/AsyncTask as deprecated (but mentioned as interview topics).
• Clarified background execution, broadcasts and services: manifest broadcast restrictions (Android 8.0+), startForegroundService() behavior, WorkManager as the practical cross-API replacement, and PendingIntent FLAG_IMMUTABLE/FLAG_MUTABLE requirement (Android 12+).
• Filled missing practical topics and tooling: DataStore (Preferences/Proto), bitmap decoding and pooling recommendations, Jetpack Security / Keystore, onTrimMemory handling, LeakCanary/Memory Profiler usage, NotificationChannel and POST_NOTIFICATIONS requirement, ART (AOT+JIT with profile-guided compilation), and other small clarifications throughout.

Testing

• Documentation-only changes; no unit/integration tests were added or run.
• File updated: section/android.md and changes committed (git commit completed locally).
• No automated test failures (no tests executed).

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Codex Task