Add E2E tests for Image visual examples (#55964)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55964

Add screenshot E2E tests for 7 Image examples that previously lacked E2E coverage:
static-image, tint-color, opacity, nesting-content, nesting-image-background,
blur-radius, and base64-image.

- Added `name` and `testID` to each example in ImageExample.js
- 6 tests are cross-platform (excludedPlatforms: ['mac'])
- 1 test is iOS-only (base64-image)
- animated-gif test was removed due to persistent infra failure preventing
  screenshot capture; name and testID were still added to the source

Reviewed By: cortinico

Differential Revision: D95371702

fbshipit-source-id: c839e26425914f9b18722f313d19c20b50d7fe84