Prepare 21st Capital branch for v8 #8

Job	Run time
linter	34s
linter_gui	1m 50s
unit_tests (1.63, ubuntu-latest)	2m 54s
unit_tests (1.63, macOS-latest)	2m 30s
unit_tests (1.63, windows-latest)	4m 39s
unit_tests (nightly, ubuntu-latest)	1m 1s
unit_tests (nightly, macOS-latest)	1m 42s
unit_tests (nightly, windows-latest)	2m 11s
unit_tests_gui (1.71.1, ubuntu-latest)	3m 38s
unit_tests_gui (1.71.1, macOS-latest)	2m 43s
unit_tests_gui (1.71.1, windows-latest)	6m 28s
unit_tests_gui (nightly, ubuntu-latest)	2m 56s
unit_tests_gui (nightly, macOS-latest)	2m 35s
unit_tests_gui (nightly, windows-latest)	5m 28s
	41m 9s

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