Add nonblocking open support to Dialog #729

Job	Run time
Unit tests (ubuntu-latest, 3.8, 5, pyqt)	2m 53s
Unit tests (ubuntu-latest, 3.8, 5, pyside)	3m 2s
Unit tests (ubuntu-latest, 3.9, 5, pyqt)	2m 44s
Unit tests (ubuntu-latest, 3.9, 5, pyside)	3m 29s
Unit tests (ubuntu-latest, 3.10, 5, pyqt)	3m 1s
Unit tests (ubuntu-latest, 3.10, 6, pyqt)	3m 4s
Unit tests (ubuntu-latest, 3.11, 6, pyqt)	2m 53s
Unit tests (ubuntu-latest, 3.12, 6, pyqt)	3m 32s
Unit tests (windows-latest, 3.8, 5, pyqt)	4m 9s
Unit tests (windows-latest, 3.8, 5, pyside)	4m 32s
Unit tests (windows-latest, 3.9, 5, pyqt)	4m 19s
Unit tests (windows-latest, 3.9, 5, pyside)	4m 14s
Unit tests (windows-latest, 3.10, 5, pyqt)	4m 43s
Unit tests (windows-latest, 3.10, 6, pyqt)	4m 53s
Unit tests (windows-latest, 3.10, 6, pyside)	4m 56s
Unit tests (windows-latest, 3.11, 6, pyqt)	4m 51s
Unit tests (windows-latest, 3.11, 6, pyside)	4m 57s
Unit tests (windows-latest, 3.12, 6, pyqt)	4m 30s
Unit tests (macos-latest, 3.10, 5, pyqt)	3m 52s
Unit tests (macos-latest, 3.10, 6, pyqt)	3m 1s
Unit tests (macos-latest, 3.10, 6, pyside)	2m 47s
Unit tests (macos-latest, 3.11, 6, pyqt)	2m 49s
Unit tests (macos-latest, 3.11, 6, pyside)	3m 14s
Unit tests (macos-latest, 3.12, 6, pyqt)	2m 26s
	1h 28m 51s

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