Fix Android display metrics refresh on density changes

[nikhilpakhloo]

Summary

Fixes Android display metrics getting stale when a React Native surface moves to a display/window with a different density, such as Samsung DeX, freeform windows, external monitors, or ChromeOS.

DisplayMetricsHolder was initialized once and could keep using the main display density, while Fabric/root layout could use the current display density. This caused text sp -> px conversion to use the wrong scale, making text render too large and clip.

Changes

• Refresh DisplayMetricsHolder when Android configuration/display metrics change.
• Request relayout and emit Dimensions updates when display metrics change.
• Keep Fabric pixel density in sync with refreshed display metrics.
• Initialize root-view display metrics from the visual/root context instead of application context.
• Add tests for display metrics change detection.

Changelog:

[ANDROID] [FIXED] - Keep display metrics in sync when Android display density changes

Test Plan

• Ran ktfmtFormat.
• Ran git diff --check.
• Attempted targeted Android unit test, but local Windows codegen setup failed before tests ran due to buildCodegenCLI / tar path handling.