ci: support optional Unreal UI automation

[kavmur]

Fixes: N/A

What was the problem/requirement? (What/Why)

The Unreal Engine integration workflow needs to optionally enable its UI automation (spec tests) suite in the existing CodeBuild integration project. The shared workflow did not expose or forward a setting for this behavior.

What was the solution? (How)

Added an optional boolean run_ui_automation input to the reusable integration workflow and forwarded it to CodeBuild as RUN_UI_AUTOMATION.

The input defaults to false, so existing callers and normal integration runs retain their current behavior.

What is the impact of this change?

There is no behavior change for existing callers.

Repositories can explicitly opt into Unreal UI automation by setting run_ui_automation: true. CodeBuild projects that do not use the variable are unaffected.

How was this change tested?

• Validated the tests in dev:
  • plugin and C++ tests rebuilt from source;
  • 2 Python integration tests passed;
  • 45 UI automation tests passed;
  • Unreal Editor exited with code 0.

Was this change documented?

No documentation change is required for this backward-compatible reusable workflow input.

Is this a breaking change?

No. The new input is optional and defaults to false.