[feature] Rename V4 `app` dir to => `src` @W-18895152@ #10948

Job	Run time
changelog-check	27s
generated (typescript-minimal-test-project)	2m 35s
generated (express-minimal-test-project)	2m 33s
generated (retail-react-app-test-project)	2m 52s
bundle-sizes	3m 19s
generated-windows (retail-react-app-test-project)	7m 2s
generated-windows (express-minimal-test-project)	7m 13s
generated-windows (typescript-minimal-test-project)	6m 33s
pwa-kit (20, 8)	6m 44s
pwa-kit (18, 10)	9m 26s
pwa-kit (18, 8)	7m 31s
pwa-kit (20, 10)	8m 37s
pwa-kit (20, 11)	6m 57s
pwa-kit (18, 9)	7m 14s
pwa-kit (22, 8)	6m 28s
pwa-kit (20, 9)	6m 41s
pwa-kit (22, 11)	6m 29s
pwa-kit-windows (18, 9)	12m 27s
pwa-kit-windows (18, 8)	11m 17s
pwa-kit (22, 9)	6m 12s
pwa-kit-windows (20, 9)	11m 58s
pwa-kit-windows (20, 10)	14m 52s
pwa-kit-windows (20, 8)	10m 39s
pwa-kit-windows (18, 10)	15m 36s
pwa-kit-windows (22, 8)	10m 13s
pwa-kit (22, 10)	8m 44s
pwa-kit-windows (22, 11)	9m 52s
pwa-kit-windows (20, 11)	10m 53s
pwa-kit-windows (22, 10)	14m 7s
pwa-kit-windows (22, 9)	9m 59s
	4h 5m 30s

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