[service] Remove getBallastSize from service #21187

Job	Run time
govulncheck	24s
setup-environment	17s
unittest-matrix (ubuntu-latest, ~1.22)	2m 21s
checks	1m 54s
lint	3m 41s
unittest-matrix (ubuntu-latest, ~1.21.12)	2m 17s
cross-build-collector (darwin, amd64)	42s
test-coverage	5m 59s
cross-build-collector (darwin, arm64)	43s
cross-build-collector (linux, 386)	43s
cross-build-collector (linux, amd64)	38s
cross-build-collector (linux, arm64)	37s
cross-build-collector (linux, ppc64le)	43s
cross-build-collector (linux, arm, 7)	37s
cross-build-collector (linux, s390x)	45s
cross-build-collector (windows, 386)	46s
cross-build-collector (windows, amd64)	37s
unittest	1s
	23m 45s

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