Simplify logic in boundedMemoryQueue, use channels len/cap #15388

Job	Run time
setup-environment	12s
govulncheck	52s
test-coverage	1m 0s
checks	2m 34s
lint	2m 52s
cross-build-collector (darwin, amd64)	1m 6s
unittest-matrix (~1.21.3)	1m 12s
cross-build-collector (darwin, arm64)	57s
cross-build-collector (linux, 386)	39s
unittest-matrix (~1.20.10)	57s
cross-build-collector (linux, amd64)	1m 3s
cross-build-collector (linux, arm64)	1m 12s
cross-build-collector (linux, ppc64le)	57s
cross-build-collector (linux, arm, 7)	1m 25s
cross-build-collector (linux, s390x)	33s
cross-build-collector (windows, 386)	39s
cross-build-collector (windows, amd64)	36s
unittest	1s
	18m 47s

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