Improved speed of instrumentation tests on CI

[LachlanMcKee]

Description

Improved performance and reliability of instrumentation tests on CI.

This was done by:

• Splitting the screenshot tests into a separate job.
• Use Test Orchestrator to remove any state between tests causing flakiness.
• Use Gradle Managed devices instead of the ReactiveCircus Emulator which appears to be faster.

Note:

• The height of the screenshots changed due to use the 'adt' emulator which is typically faster.

Check list

• I have updated CHANGELOG.md if required.
• I have updated documentation if required.