feat(protocol): Span Batch Element #687

Job	Run time
docs	36s
cfg-check	30s
clippy	37s
doctest	52s
feature-checks	1m 19s
feature-powerset	1m 18s
no-std	37s
fmt	14s
test stable --no-default-features	51s
wasm-unknown	26s
wasm-wasi	30s
test stable	50s
test stable --all-features	1m 8s
test nightly --no-default-features	41s
test nightly	48s
test nightly --all-features	1m 4s
test 1.81 --no-default-features	32s
test 1.81	54s
	13m 47s

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