ci: run full UI suite on PR when AuthFlowTester changes

[wmathurin]

Summary

• When a PR modifies any file under `native/NativeSampleApps/AuthFlowTester/`, the CI now runs the full UI suite (all test classes, including `MultiUserLoginTests`) instead of the fixed 7-test smoke subset.
• Unrelated PRs continue to use the fast 7-test subset with a 10-minute timeout.
• Full-suite run uses a 30-minute timeout on API 36 / MediumPhone.arm.

How it works

• `TestOrchestrator.rb` detects whether any changed file starts with `native/NativeSampleApps/AuthFlowTester/` and emits a `run_all_ui_tests` boolean output.
• `pr.yaml` propagates that output to `reusable-ui-workflow.yaml` as a new `run_all_ui_tests` input.
• In `reusable-ui-workflow.yaml`, the existing "Run PR Tests" step is gated on `!run_all_ui_tests`; a new "Run All UI Tests" step runs when `run_all_ui_tests` is true, with no `--test-targets` filter so all classes (including `MultiUserLoginTests`) execute.
• The `results-dir` name is unchanged (`authflowtester-pr-build-${RUN_NUMBER}`) so the downstream "Copy Test Results" and "Test Report" steps require no changes.

Test plan

• Verify a PR touching only `libs/` still runs the 7-test subset
• Verify a PR touching `native/NativeSampleApps/AuthFlowTester/` triggers the full suite including `MultiUserLoginTests`