Bump version to "v21.0.0-next.9" with changelog. #9387

Job	Run time
lint	2m 21s
analyze	5s
build	5m 3s
build-e2e-windows-subset	5m 13s
e2e-package-managers (ubuntu-latest, 22, yarn, 0)	7m 32s
e2e-package-managers (ubuntu-latest, 22, yarn, 1)	6m 17s
e2e-package-managers (ubuntu-latest, 22, pnpm, 2)	5m 49s
e2e-package-managers (ubuntu-latest, 22, pnpm, 0)	5m 51s
e2e-package-managers (ubuntu-latest, 22, yarn, 2)	7m 3s
e2e-package-managers (ubuntu-latest, 22, pnpm, 1)	4m 28s
test	3m 40s
e2e-snapshots	0s
e2e (ubuntu-latest, 22, npm, 1)	12m 5s
e2e (ubuntu-latest, 22, npm, 2)	11m 24s
e2e (ubuntu-latest, 22, npm, 0)	11m 20s
e2e (ubuntu-latest, 22, esbuild, 1)	9m 42s
e2e (ubuntu-latest, 22, npm, 4)	9m 1s
e2e (ubuntu-latest, 22, esbuild, 0)	8m 23s
e2e (ubuntu-latest, 22, esbuild, 3)	8m 23s
e2e (ubuntu-latest, 22, npm, 5)	10m 5s
e2e (ubuntu-latest, 22, esbuild, 5)	6m 55s
e2e (ubuntu-latest, 22, esbuild, 4)	6m 35s
e2e (ubuntu-latest, 22, esbuild, 2)	8m 52s
e2e (ubuntu-latest, 22, npm, 3)	8m 39s
e2e-windows-subset	5m 21s
	2h 50m 7s

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