Fix Android `scenario_app` to actually run and block on CI (#50414)

https://github.com/flutter/engine/pull/50414/commits/20337eaea438e505d4bd215b4e84362fa9935d2d
(now reverted) intentionally re-introduced a bug
(https://github.com/flutter/engine/pull/49938) on a now working test
runner, and verified that (with some fixes in this PR), we can now catch
regressions on CI with SkiaGold:

---

<details>

<summary>ExternalTextureTests_testCanvasSurface.png</summary>

This test shows that what previously was a picture has been reduced down
to a single stretched pixel.

**BEFORE**:


![ExternalTextureTests_testCanvasSurface](https://github.com/flutter/engine/assets/168174/1509ea21-2887-4a3b-b200-b857bbfb8304)

**AFTER**:


![ExternalTextureTests_testCanvasSurface](https://github.com/flutter/engine/assets/168174/d9ae19c8-dd39-4e7f-859c-5d82bd1ba0a3)

</details>

<details>

<summary>ExternalTextureTests_testRotatedMediaSurface_180.png</summary>

Similar to above, but shows _another_ bug (kClamp versus kRepeat)

**BEFORE**:


![ExternalTextureTests_testRotatedMediaSurface_180](https://github.com/flutter/engine/assets/168174/fee5bc8d-749f-4a59-976a-a573515fecea)

**AFTER**:


![ExternalTextureTests_testRotatedMediaSurface_180](https://github.com/flutter/engine/assets/168174/a5249f70-22b4-4d36-8b63-e88c8a6846fe)/cc

</details>

---

This PR now makes the `scenario_test` useful and blocking for Android
engine rolls:

- Add support for connecting to SkiaGold by depending on `goldctl` in
the appropriate configs.
- Add some useful local debugging flags for skipping SkiaGold or running
specific tests (not used by default).
- Failing to connect to Skia gold is now a test failure.
4 files changed
tree: d1bedd2079e1f4abc709c92523ed5b06cc5a3e17
  1. .github/
  2. assets/
  3. benchmarking/
  4. build/
  5. ci/
  6. common/
  7. display_list/
  8. docs/
  9. examples/
  10. flow/
  11. flutter_frontend_server/
  12. flutter_vma/
  13. fml/
  14. impeller/
  15. lib/
  16. runtime/
  17. shell/
  18. skia/
  19. sky/
  20. testing/
  21. third_party/
  22. tools/
  23. vulkan/
  24. wasm/
  25. web_sdk/
  26. .ci.yaml
  27. .clang-format
  28. .clang-tidy
  29. .gitattributes
  30. .gitignore
  31. .pylintrc
  32. .style.yapf
  33. analysis_options.yaml
  34. AUTHORS
  35. BUILD.gn
  36. CODEOWNERS
  37. CONTRIBUTING.md
  38. DEPS
  39. Doxyfile
  40. LICENSE
  41. README.md
README.md

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