[bug][mdatagen] Auto-enable v1 metrics when legacy is enabled #41380

Job	Run time
setup-environment	8s
checks	2m 46s
test-coverage	11m 33s
lint	16m 15s
unittest-matrix (ubuntu-latest, oldstable)	7m 4s
govulncheck	3m 13s
unittest-matrix (ubuntu-latest, stable)	6m 40s
cross-build-collector (darwin, amd64)	54s
cross-build-collector (darwin, arm64)	53s
cross-build-collector (linux, arm64)	54s
cross-build-collector (linux, ppc64le)	35s
cross-build-collector (windows, 386)	45s
cross-build-collector (aix, ppc64)	53s
cross-build-collector (js, wasm)	53s
cross-build-collector (windows, arm64)	58s
cross-build-collector (linux, s390x)	54s
cross-build-collector (linux, amd64)	1m 0s
cross-build-collector (linux, arm, 7)	55s
cross-build-collector (windows, amd64)	56s
cross-build-collector (linux, riscv64)	53s
cross-build-collector (linux, 386)	54s
unittest	3s
	59m 59s

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