Refactor to decouple plugins and extensions from main branch

[Himanth-reddy]

This pull request removes all code and dependencies related to the sideloadable plugin system from the project. This includes the removal of plugin-related Gradle dependencies, ProGuard rules, data storage, and code safety checks, as well as the removal of plugin repository and scraper sync logic from the cloud sync subsystem. The result is a significant simplification of the codebase, eliminating all support for user-installed plugins.

The most important changes are:

Build system and dependency cleanup:

• Removed all plugin system dependencies for the sideload flavor from app/build.gradle.kts, including QuickJS, Jackson, NiceHttp, Conscrypt, CloudStream, Rhino, RE2J, and Crypto-JS libraries. [1] [2]
• Removed the FEATURE_PLUGINS_ENABLED build config field from all build variants in app/build.gradle.kts. [1] [2]

Code and data layer removal:

• Deleted the PluginDataStore, PluginSafety, and TestDiagnostics classes, fully removing plugin-related data storage, plugin validation, and diagnostics code. [1] [2] [3]

Cloud sync and integration removal:

• Removed all plugin repository and scraper sync logic from CloudSyncRepository, including both backup and restore flows, and the associated dependency injection. [1] [2] [3]

ProGuard configuration:

• Removed ProGuard rules and keep directives related to the plugin runtime, CloudStream, and Jackson from app/proguard-rules.pro.

These changes fully remove sideloadable plugin support and all related infrastructure from the project.… to plugin-extentions branch)