Add support for third-party GUI framework plugins #3550

Job	Run time
Check towncrier / Towncrier Checks	24s
Pre-commit checks / Pre-commit Checks	46s
Python package / Create Python Package	1m 35s
Unit tests (macos, 3.8)	2m 2s
Unit tests (macos, 3.9)	3m 14s
Unit tests (macos, 3.10)	2m 7s
Unit tests (macos, 3.11)	2m 32s
Unit tests (macos, 3.12)	3m 2s
Unit tests (ubuntu, 3.8)	1m 22s
Unit tests (ubuntu, 3.9)	1m 43s
Unit tests (ubuntu, 3.10)	1m 14s
Unit tests (ubuntu, 3.11)	1m 8s
Unit tests (ubuntu, 3.12)	2m 37s
Unit tests (windows, 3.8)	2m 41s
Unit tests (windows, 3.9)	3m 4s
Unit tests (windows, 3.10)	2m 58s
Unit tests (windows, 3.11)	2m 6s
Unit tests (windows, 3.12)	3m 43s
Unit tests (windows, winstore3.12, false)	3m 0s
Project coverage	44s
Build app (ppb, macos-latest) / Verify App Build	2m 36s
Build app (ppb, ubuntu-22.04) / Verify App Build	5m 8s
Build app (ppb, windows-latest) / Verify App Build	2m 30s
Build app (pygame, macos-latest) / Verify App Build	2m 56s
Build app (pygame, ubuntu-22.04) / Verify App Build	5m 7s
Build app (pygame, windows-latest) / Verify App Build	2m 41s
Build app (pyside2, ubuntu-22.04) / Verify App Build	2m 34s
Build app (pyside2, windows-latest) / Verify App Build	2m 7s
Build app (pyside6, macos-latest) / Verify App Build	2m 25s
Build app (pyside6, ubuntu-22.04) / Verify App Build	5m 4s
Build app (pyside6, windows-latest) / Verify App Build	2m 48s
Build app (toga, macos-latest) / Verify App Build	5m 3s
Build app (toga, ubuntu-22.04) / Verify App Build	5m 5s
Build app (toga, windows-latest) / Verify App Build	5m 1s
	1h 33m 7s

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