[service] Remove getBallastSize from service #21231

Job	Run time
govulncheck	40s
setup-environment	8s
test-coverage	6m 23s
lint	3m 54s
checks	2m 7s
unittest-matrix (ubuntu-latest, ~1.22)	2m 34s
unittest-matrix (ubuntu-latest, ~1.21.12)	2m 20s
cross-build-collector (darwin, amd64)	42s
cross-build-collector (darwin, arm64)	38s
cross-build-collector (linux, 386)	42s
cross-build-collector (linux, amd64)	43s
cross-build-collector (linux, arm64)	39s
cross-build-collector (linux, ppc64le)	44s
cross-build-collector (linux, arm, 7)	35s
cross-build-collector (linux, s390x)	41s
cross-build-collector (windows, 386)	47s
cross-build-collector (windows, amd64)	48s
unittest	1s
	25m 6s

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