chore: Add integration tests for Android

[tustanivsky]

This PR adds Android integration tests for the Sentry Unreal SDK using PowerShell's Pester framework. The tests validate end-to-end functionality by running the SentryPlayground sample application on mobile devices and verifying that events are properly captured and sent to Sentry.

It includes the necessary CI workflows and test scripts for both local (adb) and cloud (SauceLabs) execution.

The motivation for using SauceLabs Real Device Cloud to run tests in CI pipeline is the current limitation of Android emulators which do not support the rendering backends required by Unreal applications.

Changes

• Added integration-test-android.yml to run Android integration tests on SauceLabs.
• Updated ci.yml to include the new Android test workflow.
• Added Test Scripts:
  • Integration.Tests.Android.SauceLabs.ps1 for running tests on SauceLabs devices.
  • Integration.Tests.Android.Adb.ps1 for running tests locally via adb.
• Expanded README.md with comprehensive instructions for running Android tests locally and via SauceLabs, including required environment variables and prerequisites.
• Added SAUCE_USERNAME and SAUCE_ACCESS_KEY secrets to the repo.

Related to:

• #1127
• #1131

Closes #964

#skip-changelog