[exporterhelper] Add span links across batcher when merging multiple … #29651

Job	Run time
govulncheck	33s
setup-environment	12s
unittest-matrix (ubuntu-latest, ~1.24)	2m 40s
lint	4m 49s
unittest-matrix (ubuntu-latest, ~1.23)	2m 35s
checks	2m 27s
cross-build-collector (aix, ppc64)	42s
test-coverage	8m 25s
cross-build-collector (darwin, amd64)	47s
cross-build-collector (darwin, arm64)	41s
cross-build-collector (linux, 386)	49s
cross-build-collector (linux, amd64)	46s
cross-build-collector (linux, arm64)	51s
cross-build-collector (linux, ppc64le)	47s
cross-build-collector (linux, arm, 7)	49s
cross-build-collector (linux, s390x)	42s
cross-build-collector (windows, 386)	42s
cross-build-collector (windows, amd64)	47s
unittest	1s
	30m 5s

Provide feedback