[feature] Rename V4 `app` dir to => `src` @W-18895152@ #10760

Job	Run time
changelog-check	22s
generated (express-minimal-test-project)	2m 19s
generated (typescript-minimal-test-project)	2m 22s
generated (retail-react-app-test-project)	2m 34s
bundle-sizes	3m 4s
generated-windows (express-minimal-test-project)	5m 41s
generated-windows (typescript-minimal-test-project)	5m 48s
generated-windows (retail-react-app-test-project)	5m 1s
pwa-kit (18, 9)	17m 12s
pwa-kit (18, 10)	19m 6s
pwa-kit (20, 8)	16m 2s
pwa-kit (18, 8)	16m 59s
pwa-kit (20, 9)	15m 59s
pwa-kit (20, 10)	17m 32s
pwa-kit (22, 8)	15m 2s
pwa-kit (22, 9)	14m 56s
pwa-kit-windows (18, 10)	26m 21s
pwa-kit (22, 10)	16m 42s
pwa-kit-windows (18, 9)	24m 1s
pwa-kit (22, 11)	14m 53s
pwa-kit-windows (18, 8)	24m 4s
pwa-kit-windows (20, 8)	22m 30s
pwa-kit-windows (22, 8)	21m 48s
pwa-kit (20, 11)	15m 46s
pwa-kit-windows (20, 9)	24m 22s
pwa-kit-windows (20, 10)	25m 44s
pwa-kit-windows (22, 10)	24m 35s
pwa-kit-windows (22, 9)	22m 54s
pwa-kit-windows (20, 11)	22m 9s
pwa-kit-windows (22, 11)	21m 7s
	7h 46m 55s

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