Make the option `WithErrorUnused` enabled by default when unmarshaling configuration #16352

Job	Run time
govulncheck	24s
setup-environment	13s
checks	1m 25s
lint	3m 4s
test-coverage	2m 46s
unittest-matrix (~1.21.5)	2m 35s
cross-build-collector (darwin, amd64)	40s
unittest-matrix (~1.20.12)	2m 6s
cross-build-collector (darwin, arm64)	40s
cross-build-collector (linux, 386)	40s
cross-build-collector (linux, amd64)	40s
cross-build-collector (linux, arm64)	40s
cross-build-collector (linux, ppc64le)	44s
cross-build-collector (linux, arm, 7)	45s
cross-build-collector (linux, s390x)	33s
cross-build-collector (windows, 386)	34s
cross-build-collector (windows, amd64)	37s
unittest	1s
	19m 7s

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